Fixes memory leak in HazelcastAsyncMultiMap

Calling ClusterManager.getAsyncMultiMap multiple times can leak memory has the map listener is still registered.

See vert-x3/issues#316

src/main/java/io/vertx/spi/cluster/hazelcast/impl/HazelcastAsyncMultiMap.java

@@ -44,6 +44,7 @@ public class HazelcastAsyncMultiMap<K, V> implements AsyncMultiMap<K, V>, EntryL
 
   private final VertxInternal vertx;
   private final com.hazelcast.core.MultiMap<K, V> map;
+  private final String listenerRegistrationId;
   private final TaskQueue taskQueue = new TaskQueue();
 
 
@@ -62,7 +63,7 @@ public class HazelcastAsyncMultiMap<K, V> implements AsyncMultiMap<K, V>, EntryL
   public HazelcastAsyncMultiMap(Vertx vertx, com.hazelcast.core.MultiMap<K, V> map) {
     this.vertx = (VertxInternal) vertx;
     this.map = map;
-    map.addEntryListener(this, true);
+    listenerRegistrationId = map.addEntryListener(this, true);
   }
 
   @Override
@@ -83,6 +84,11 @@ public void removeAllMatching(Predicate<V> p, Handler<AsyncResult<Void>> complet
     }, taskQueue, completionHandler);
   }
 
+  @Override
+  public void close() {
+    map.removeEntryListener(listenerRegistrationId);
+  }
+
   @Override
   public void add(K k, V v, Handler<AsyncResult<Void>> completionHandler) {
     vertx.getOrCreateContext().executeBlocking(fut -> {