Fix testCloudProfile to connect to "localhost"

When we don't specify the `host` property for the
`CachingConnectionFactory`, it is selected by the
`InetAddress.getLocalHost().getHostName()`, which might not be
"localhost" as it is allowed for the `guest` user on RabbitMQ.
This also may cause some unexpected loop-backs on the network interface
during connection attempt

**Cherry-pick to 1.3.x**

spring-cloud-stream-binder-rabbit/src/test/java/org/springframework/cloud/stream/binder/rabbit/integration/RabbitBinderModuleTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2017 the original author or authors.
+ * Copyright 2015-2018 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.
@@ -291,7 +291,7 @@ public class RabbitBinderModuleTests {
 		public Cloud cloud() {
 			Cloud cloud = mock(Cloud.class);
 
-			willReturn(new CachingConnectionFactory())
+			willReturn(new CachingConnectionFactory("localhost"))
 							.given(cloud)
 							.getSingletonServiceConnector(ConnectionFactory.class, null);