Various polishing and optimizations

* Check for `null` package in the `JacksonJsonUtils`.
Also don't call `this.delegate.typeFromId()` the second time
* Increase wait timeout in the `QueueChannelTests`
* Check `ZookeeperMetadataStore.addListener()` for `null`

**Cherry-pick to 4.3.x**

spring-integration-core/src/test/java/org/springframework/integration/channel/QueueChannelTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -58,7 +58,7 @@ public class QueueChannelTests {
 		}).start();
 		assertFalse(messageReceived.get());
 		channel.send(new GenericMessage<String>("testing"));
-		latch.await(1000, TimeUnit.MILLISECONDS);
+		latch.await(10000, TimeUnit.MILLISECONDS);
 		assertTrue(messageReceived.get());
 	}