Fix Race in ReferenceCountedOpenSslEngine

Motivation:
ReferenceCountedOpenSslEngine is careful to lock access to `ssl`
almost everywhere (manually verified) *except* in the constructor.
Since `ssl` is non-final, it does not enjoy automatic thread safety
of the code that uses it.  Specifically, that means netty tcnative
code is not thread safe.

Modifications:

Ensure that all ssl engine intialization and variables related to
it are properly synchronized  by adding in the constructor.

Result:
Less noisy race detector.

Notes:
The specific racing threads are:
```
  Read of size 8 at 0x7b5400019ff8 by thread T52 (mutexes: write M215300):
    #0 ssl_do_info_callback .../src/ssl/ssl_lib.c:2602:24 (f077793ecd812aeebb37296c987f655c+0x23c6834)
    netty#1 ssl_process_alert .../src/ssl/tls_record.c:473:3 (f077793ecd812aeebb37296c987f655c+0x23a5346)
    netty#2 tls_open_record .../src/ssl/tls_record.c:338:12 (f077793ecd812aeebb37296c987f655c+0x23a5289)
    netty#3 ssl3_get_record .../src/ssl/s3_pkt.c:146:7 (f077793ecd812aeebb37296c987f655c+0x23a3da0)
    netty#4 ssl3_read_app_data .../src/ssl/s3_pkt.c:388:17 (f077793ecd812aeebb37296c987f655c+0x23a368f)
    netty#5 ssl_read_impl .../src/ssl/ssl_lib.c:722:15 (f077793ecd812aeebb37296c987f655c+0x23c0895)
    netty#6 SSL_read .../src/ssl/ssl_lib.c:743:10 (f077793ecd812aeebb37296c987f655c+0x23c075b)
    netty#7 netty_internal_tcnative_SSL_readFromSSL .../netty_tcnative/openssl-dynamic/src/main/c/ssl.c:946:12 (f077793ecd812aeebb37296c987f655c+0x23827f7)
    netty#8 <null> <null> (0x7fc0760193be)
    netty#9 io.netty.handler.ssl.ReferenceCountedOpenSslEngine.readPlaintextData(Ljava/nio/ByteBuffer;)I (ReferenceCountedOpenSslEngine.java:449)
    netty#10 io.netty.handler.ssl.ReferenceCountedOpenSslEngine.unwrap([Ljava/nio/ByteBuffer;II[Ljava/nio/ByteBuffer;II)Ljavax/net/ssl/SSLEngineResult; (ReferenceCountedOpenSslEngine.java:882)
    netty#11 io.netty.handler.ssl.ReferenceCountedOpenSslEngine.unwrap([Ljava/nio/ByteBuffer;[Ljava/nio/ByteBuffer;)Ljavax/net/ssl/SSLEngineResult; (ReferenceCountedOpenSslEngine.java:985)
    netty#12 io.netty.handler.ssl.ReferenceCountedOpenSslEngine.unwrap(Ljava/nio/ByteBuffer;Ljava/nio/ByteBuffer;)Ljavax/net/ssl/SSLEngineResult; (ReferenceCountedOpenSslEngine.java:1028)
    netty#13 io.netty.handler.ssl.SslHandler$SslEngineType$1.unwrap(Lio/netty/handler/ssl/SslHandler;Lio/netty/buffer/ByteBuf;IILio/netty/buffer/ByteBuf;)Ljavax/net/ssl/SSLEngineResult; (SslHandler.java:206)
    netty#14 io.netty.handler.ssl.SslHandler.unwrap(Lio/netty/channel/ChannelHandlerContext;Lio/netty/buffer/ByteBuf;II)Z (SslHandler.java:1162)
    netty#15 io.netty.handler.ssl.SslHandler.decode(Lio/netty/channel/ChannelHandlerContext;Lio/netty/buffer/ByteBuf;Ljava/util/List;)V (SslHandler.java:1084)
    netty#16 io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(Lio/netty/channel/ChannelHandlerContext;Lio/netty/buffer/ByteBuf;Ljava/util/List;)V (ByteToMessageDecoder.java:489)
    netty#17 io.netty.handler.codec.ByteToMessageDecoder.callDecode(Lio/netty/channel/ChannelHandlerContext;Lio/netty/buffer/ByteBuf;Ljava/util/List;)V (ByteToMessageDecoder.java:428)
    netty#18 io.netty.handler.codec.ByteToMessageDecoder.channelRead(Lio/netty/channel/ChannelHandlerContext;Ljava/lang/Object;)V (ByteToMessageDecoder.java:265)
    netty#19 io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(Ljava/lang/Object;)V (AbstractChannelHandlerContext.java:362)
    netty#20 io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(Lio/netty/channel/AbstractChannelHandlerContext;Ljava/lang/Object;)V (AbstractChannelHandlerContext.java:348)
    netty#21 io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(Ljava/lang/Object;)Lio/netty/channel/ChannelHandlerContext; (AbstractChannelHandlerContext.java:340)
    netty#22 io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(Lio/netty/channel/ChannelHandlerContext;Ljava/lang/Object;)V (DefaultChannelPipeline.java:1334)
    netty#23 io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(Ljava/lang/Object;)V (AbstractChannelHandlerContext.java:362)
    netty#24 io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(Lio/netty/channel/AbstractChannelHandlerContext;Ljava/lang/Object;)V (AbstractChannelHandlerContext.java:348)
    netty#25 io.netty.channel.DefaultChannelPipeline.fireChannelRead(Ljava/lang/Object;)Lio/netty/channel/ChannelPipeline; (DefaultChannelPipeline.java:926)
    netty#26 io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read()V (AbstractNioByteChannel.java:134)
    netty#27 io.netty.channel.nio.NioEventLoop.processSelectedKey(Ljava/nio/channels/SelectionKey;Lio/netty/channel/nio/AbstractNioChannel;)V (NioEventLoop.java:644)
    netty#28 io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized()V (NioEventLoop.java:579)
    netty#29 io.netty.channel.nio.NioEventLoop.processSelectedKeys()V (NioEventLoop.java:496)
    netty#30 io.netty.channel.nio.NioEventLoop.run()V (NioEventLoop.java:458)
    netty#31 io.netty.util.concurrent.SingleThreadEventExecutor$5.run()V (SingleThreadEventExecutor.java:858)
    netty#32 io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run()V (DefaultThreadFactory.java:138)
    netty#33 java.lang.Thread.run()V (Thread.java:745)
    netty#34 (Generated Stub)

  Previous write of size 8 at 0x7b5400019ff8 by thread T97:
    #0 SSL_CTX_set_info_callback .../ssl/ssl_session.c:1136:22 (f077793ecd812aeebb37296c987f655c+0x23bd621)
    netty#1 netty_internal_tcnative_SSL_newSSL .../netty_tcnative/openssl-dynamic/src/main/c/ssl.c:830:5 (f077793ecd812aeebb37296c987f655c+0x2382306)
    netty#2 <null> <null> (0x7fc0760193be)
    netty#3 io.netty.handler.ssl.ReferenceCountedOpenSslEngine.<init>(Lio/netty/handler/ssl/ReferenceCountedOpenSslContext;Lio/netty/buffer/ByteBufAllocator;Ljava/lang/String;IZ)V (ReferenceCountedOpenSslEngine.java:237)
    netty#4 io.netty.handler.ssl.OpenSslEngine.<init>(Lio/netty/handler/ssl/OpenSslContext;Lio/netty/buffer/ByteBufAllocator;Ljava/lang/String;I)V (OpenSslEngine.java:31)
    netty#5 io.netty.handler.ssl.OpenSslContext.newEngine0(Lio/netty/buffer/ByteBufAllocator;Ljava/lang/String;I)Ljavax/net/ssl/SSLEngine; (OpenSslContext.java:49)
    netty#6 io.netty.handler.ssl.ReferenceCountedOpenSslContext.newEngine(Lio/netty/buffer/ByteBufAllocator;Ljava/lang/String;I)Ljavax/net/ssl/SSLEngine; (ReferenceCountedOpenSslContext.java:409)
    netty#7 io.netty.handler.ssl.ReferenceCountedOpenSslContext.newEngine(Lio/netty/buffer/ByteBufAllocator;)Ljavax/net/ssl/SSLEngine; (ReferenceCountedOpenSslContext.java:423)
    netty#8 io.grpc.netty.ProtocolNegotiators$ServerTlsHandler.handlerAdded(Lio/netty/channel/ChannelHandlerContext;)V (ProtocolNegotiators.java:133)
    netty#9 io.netty.channel.DefaultChannelPipeline.callHandlerAdded0(Lio/netty/channel/AbstractChannelHandlerContext;)V (DefaultChannelPipeline.java:597)
    netty#10 io.netty.channel.DefaultChannelPipeline.addLast(Lio/netty/util/concurrent/EventExecutorGroup;Ljava/lang/String;Lio/netty/channel/ChannelHandler;)Lio/netty/channel/ChannelPipeline; (DefaultChannelPipeline.java:226)
    netty#11 io.netty.channel.DefaultChannelPipeline.addLast(Lio/netty/util/concurrent/EventExecutorGroup;[Lio/netty/channel/ChannelHandler;)Lio/netty/channel/ChannelPipeline; (DefaultChannelPipeline.java:392)
    netty#12 io.netty.channel.DefaultChannelPipeline.addLast([Lio/netty/channel/ChannelHandler;)Lio/netty/channel/ChannelPipeline; (DefaultChannelPipeline.java:379)
    netty#13 io.grpc.netty.NettyServerTransport.start(Lio/grpc/internal/ServerTransportListener;)V (NettyServerTransport.java:99)
    netty#14 io.grpc.netty.NettyServer$1.initChannel(Lio/netty/channel/Channel;)V (NettyServer.java:164)
    netty#15 io.netty.channel.ChannelInitializer.initChannel(Lio/netty/channel/ChannelHandlerContext;)Z (ChannelInitializer.java:113)
    netty#16 io.netty.channel.ChannelInitializer.handlerAdded(Lio/netty/channel/ChannelHandlerContext;)V (ChannelInitializer.java:105)
    netty#17 io.netty.channel.DefaultChannelPipeline.callHandlerAdded0(Lio/netty/channel/AbstractChannelHandlerContext;)V (DefaultChannelPipeline.java:597)
    netty#18 io.netty.channel.DefaultChannelPipeline.access$000(Lio/netty/channel/DefaultChannelPipeline;Lio/netty/channel/AbstractChannelHandlerContext;)V (DefaultChannelPipeline.java:44)
    netty#19 io.netty.channel.DefaultChannelPipeline$PendingHandlerAddedTask.execute()V (DefaultChannelPipeline.java:1387)
    netty#20 io.netty.channel.DefaultChannelPipeline.callHandlerAddedForAllHandlers()V (DefaultChannelPipeline.java:1122)
    netty#21 io.netty.channel.DefaultChannelPipeline.invokeHandlerAddedIfNeeded()V (DefaultChannelPipeline.java:647)
    netty#22 io.netty.channel.AbstractChannel$AbstractUnsafe.register0(Lio/netty/channel/ChannelPromise;)V (AbstractChannel.java:506)
    netty#23 io.netty.channel.AbstractChannel$AbstractUnsafe.access$200(Lio/netty/channel/AbstractChannel$AbstractUnsafe;Lio/netty/channel/ChannelPromise;)V (AbstractChannel.java:419)
    netty#24 io.netty.channel.AbstractChannel$AbstractUnsafe$1.run()V (AbstractChannel.java:478)
    netty#25 io.netty.util.concurrent.AbstractEventExecutor.safeExecute(Ljava/lang/Runnable;)V (AbstractEventExecutor.java:163)
    netty#26 io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(J)Z (SingleThreadEventExecutor.java:403)
    netty#27 io.netty.channel.nio.NioEventLoop.run()V (NioEventLoop.java:462)
    netty#28 io.netty.util.concurrent.SingleThreadEventExecutor$5.run()V (SingleThreadEventExecutor.java:858)
    netty#29 io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run()V (DefaultThreadFactory.java:138)
    netty#30 java.lang.Thread.run()V (Thread.java:745)
    netty#31 (Generated Stub)

```

handler/src/main/java/io/netty/handler/ssl/ReferenceCountedOpenSslEngine.java

@@ -230,41 +230,45 @@ protected void deallocate() {
         this.jdkCompatibilityMode = jdkCompatibilityMode;
         Lock readerLock = context.ctxLock.readLock();
         readerLock.lock();
+        final long finalSsl;
         try {
-            ssl = SSL.newSSL(context.ctx, !context.isClient());
+            finalSsl = SSL.newSSL(context.ctx, !context.isClient());
         } finally {
             readerLock.unlock();
         }
-        try {
-            networkBIO = SSL.bioNewByteBuffer(ssl, context.getBioNonApplicationBufferSize());
+        synchronized (this) {
+            ssl = finalSsl;
+            try {
+                networkBIO = SSL.bioNewByteBuffer(ssl, context.getBioNonApplicationBufferSize());
 
-            // Set the client auth mode, this needs to be done via setClientAuth(...) method so we actually call the
-            // needed JNI methods.
-            setClientAuth(clientMode ? ClientAuth.NONE : context.clientAuth);
+                // Set the client auth mode, this needs to be done via setClientAuth(...) method so we actually call the
+                // needed JNI methods.
+                setClientAuth(clientMode ? ClientAuth.NONE : context.clientAuth);
 
-            if (context.protocols != null) {
-                setEnabledProtocols(context.protocols);
-            }
+                if (context.protocols != null) {
+                    setEnabledProtocols(context.protocols);
+                }
 
-            // Use SNI if peerHost was specified
-            // See https://github.com/netty/netty/issues/4746
-            if (clientMode && peerHost != null) {
-                SSL.setTlsExtHostName(ssl, peerHost);
-            }
+                // Use SNI if peerHost was specified
+                // See https://github.com/netty/netty/issues/4746
+                if (clientMode && peerHost != null) {
+                    SSL.setTlsExtHostName(ssl, peerHost);
+                }
 
-            if (enableOcsp) {
-                SSL.enableOcsp(ssl);
-            }
+                if (enableOcsp) {
+                    SSL.enableOcsp(ssl);
+                }
 
-            if (!jdkCompatibilityMode) {
-                SSL.setMode(ssl, SSL.getMode(ssl) | SSL.SSL_MODE_ENABLE_PARTIAL_WRITE);
-            }
+                if (!jdkCompatibilityMode) {
+                    SSL.setMode(ssl, SSL.getMode(ssl) | SSL.SSL_MODE_ENABLE_PARTIAL_WRITE);
+                }
 
-            // setMode may impact the overhead.
-            calculateMaxWrapOverhead();
-        } catch (Throwable cause) {
-            SSL.freeSSL(ssl);
-            PlatformDependent.throwException(cause);
+                // setMode may impact the overhead.
+                calculateMaxWrapOverhead();
+            } catch (Throwable cause) {
+                SSL.freeSSL(ssl);
+                PlatformDependent.throwException(cause);
+            }
         }
     }