Solve UnreachableNodeJoinsAgainSpec problem, see #3247

* UnreachableNodeJoinsAgain failed because of gated connection
* Removed default test value of retry-gate-closed-for, instead
  default from reference.conf is used, i.e. 0s
* deadLetters logging love

akka-cluster/src/multi-jvm/scala/akka/cluster/MultiNodeClusterSpec.scala

@@ -104,14 +104,18 @@ trait MultiNodeClusterSpec extends Suite with STMultiNodeSpec with WatchedByCoro
           sys.eventStream.publish(Mute(EventFilter.info(pattern = s)))
         }
 
-      Seq(".*received dead letter from.*ClientDisconnected",
-        ".*received dead letter from.*deadLetters.*PoisonPill",
-        ".*received dead letter from.*Disassociated",
-        ".*received dead letter from.*DisassociateUnderlying",
-        ".*received dead letter from.*HandleListenerRegistered",
-        ".*installing context org.jboss.netty.channel.DefaultChannelPipeline.*") foreach { s ⇒
-          sys.eventStream.publish(Mute(EventFilter.warning(pattern = s)))
-        }
+      muteDeadLetters(
+        "Heartbeat.*",
+        "GossipEnvelope.*",
+        "ClusterMetricsChanged.*",
+        "Disassociated.*",
+        "DisassociateUnderlying.*",
+        "HandleListenerRegistered.*",
+        "PoisonPill.*",
+        "DeathWatchNotification.*",
+        "NullMessage.*",
+        "InboundPayload.*")(sys)
+
     }
   }
 
@@ -119,13 +123,9 @@ trait MultiNodeClusterSpec extends Suite with STMultiNodeSpec with WatchedByCoro
     if (!sys.log.isDebugEnabled)
       sys.eventStream.publish(Mute(EventFilter.error(pattern = ".*Marking.* as UNREACHABLE.*")))
 
-  def muteDeadLetters(sys: ActorSystem = system): Unit =
-    if (!sys.log.isDebugEnabled)
-      sys.eventStream.publish(Mute(EventFilter.warning(pattern = ".*received dead letter from.*")))
-
   override def afterAll(): Unit = {
     if (!log.isDebugEnabled) {
-      muteDeadLetters()
+      muteDeadLetters()()
       system.eventStream.setLogLevel(ErrorLevel)
     }
     super.afterAll()