Fixing test failure in Continuous Integration.

ReplicationServerTest.java:
In windowProbeTest(), code only expected to receive a WindowMsg in answer to a WindowProbeMsg sent out. The twist is that it only cares about receiving a WindowMsg which means it can discard every other type of messages in the interim, particularly the ones coming from the protocol: MonitorMsgs, HeartbeatMsgs, etc. Used ReplicationTestCase.waitForSpecificMsg() to achieve this.

AssuredReplicationPluginTest.java:
Code cleanup.