DISPATCH-993: Send transmit batches more frequently
DISPATCH-993: Send transmit batches more frequently

Messages are more likely to be released during Link State transitions.
By transmitting messages during the transitions the test gets a
better mix of received and released messages.

A side benefit is that it saves ~40 seconds per test run.

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