WBL: Fix ping-pong test

Hello Vaughn,

As requested, a fix for the ping-ponging CalendarTest. Sorry for the whitespace conflicts. What happened is that other tests were publishing messages to queues using fanout exchanges (and therefore not exactly knowing which queues were picking up the messages). What I was planned to do was just clearing all queues before every test. Problem is that Java RabbitMQ Client does not support queue listing / bulk deleting. Simplest workaround I could come up with was by giving the TestExchangeListeners (as defined in EventTrackingTestCase) the time to consume leftover messages, and cleaning them just before starting the test.

Regards,
Wouter Blancquaert

Conflicts:
	iddd_common/src/test/java/com/saasovation/common/domain/model/EventTrackingTestCase.java