interop-testing: fix alts handshaking race

[YifeiZhuang]

https://travis-ci.org/github/grpc/grpc-java/jobs/758605192

io.grpc.testing.integration.AltsHandshakerTest > testAlts FAILED
    io.grpc.StatusRuntimeException: UNKNOWN
        at io.grpc.stub.ClientCalls.toStatusRuntimeException(ClientCalls.java:262)
        at io.grpc.stub.ClientCalls.getUnchecked(ClientCalls.java:243)
        at io.grpc.stub.ClientCalls.blockingUnaryCall(ClientCalls.java:156)
        at io.grpc.testing.integration.TestServiceGrpc$TestServiceBlockingStub.unaryCall(TestServiceGrpc.java:624)
        at io.grpc.testing.integration.AltsHandshakerTest.testAlts(AltsHandshakerTest.java:98)
        Caused by:
        io.grpc.netty.shaded.io.netty.handler.codec.DecoderException: java.lang.IllegalArgumentException: Invalid header field: frame size too small
            at io.grpc.netty.shaded.io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:471)
            at io.grpc.netty.shaded.io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:276)
            at io.grpc.netty.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
            at io.grpc.netty.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
            at io.grpc.netty.shaded.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
            at io.grpc.netty.shaded.io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
            at io.grpc.netty.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
            at io.grpc.netty.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
            at io.grpc.netty.shaded.io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
            at io.grpc.netty.shaded.io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:795)
            at io.grpc.netty.shaded.io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:475)
            at io.grpc.netty.shaded.io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:378)
            at io.grpc.netty.shaded.io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
            at io.grpc.netty.shaded.io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
            at io.grpc.netty.shaded.io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
            at java.lang.Thread.run(Thread.java:748)
            Caused by:
            java.lang.IllegalArgumentException: Invalid header field: frame size too small
                at com.google.common.base.Preconditions.checkArgument(Preconditions.java:142)
                at io.grpc.alts.internal.AltsTsiFrameProtector$Unprotector.handleHeader(AltsTsiFrameProtector.java:267)
                at io.grpc.alts.internal.AltsTsiFrameProtector$Unprotector.decodeFrame(AltsTsiFrameProtector.java:235)
                at io.grpc.alts.internal.AltsTsiFrameProtector$Unprotector.unprotect(AltsTsiFrameProtector.java:224)
                at io.grpc.alts.internal.AltsTsiFrameProtector.unprotect(AltsTsiFrameProtector.java:91)
                at io.grpc.alts.internal.TsiFrameHandler.decode(TsiFrameHandler.java:63)
                at io.grpc.netty.shaded.io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:501)
                at io.grpc.netty.shaded.io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:440)
                ... 15 more

[YifeiZhuang]

Related to #7847