DISPATCH-1772: Add logging to fallback dest self test
DISPATCH-1772: Add logging to fallback dest self test

 * This patch instruments the SwitchoverTest where most of the test
   failures show up

 * The on_message handler is broken up to explicitly handle receiving
   from primary and fallback receivers in phases 0 and 1

 * Add sender drain handling

This closes #1298

ErnieAllen/qpid-dispatch,apache/dispatch,mgoulish/qpid-dispatch,apache/qpid-dispatch,kgiusti/dispatch,kgiusti/dispatch,apache/qpid-dispatch,ted-ross/qpid-dispatch,ted-ross/qpid-dispatch,mgoulish/qpid-dispatch,ted-ross/qpid-dispatch,ted-ross/qpid-dispatch,apache/qpid-dispatch,apache/dispatch,ErnieAllen/qpid-dispatch,ted-ross/qpid-dispatch,mgoulish/qpid-dispatch,ChugR/qpid-dispatch,apache/qpid-dispatch,apache/qpid-dispatch,mgoulish/qpid-dispatch,apache/dispatch,mgoulish/qpid-dispatch,apache/qpid-dispatch,ErnieAllen/qpid-dispatch,ChugR/qpid-dispatch,apache/dispatch,apache/dispatch,ErnieAllen/qpid-dispatch,ErnieAllen/qpid-dispatch,kgiusti/dispatch,ted-ross/qpid-dispatch,ChugR/qpid-dispatch,kgiusti/dispatch,kgiusti/dispatch,ChugR/qpid-dispatch,ErnieAllen/qpid-dispatch,apache/dispatch,mgoulish/qpid-dispatch,apache/dispatch,kgiusti/dispatch,ChugR/qpid-dispatch,ChugR/qpid-dispatch