NO-JIRA: [Java Broker Tests] Fix race condition in TransactionTimeoutTests meaning observations of test members could yield NPE

* Reordered so that the exception listener's latch is decremented only after members for linked exception message and linked exception code.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1597595 13f79535-47bb-0310-9956-ffa450edef68