QPID-4607: C++ Broker connection limit counting fails

Repair a few small but critical errors in program logic.
Repair several misconceptions in the self test including:
* provide visibility to connections (not sessions) so that they may be closed.
* dodge names that may survive open connections from other tests.
  Tests may pass if run first but then fail if run 30th.

The whole acl.py module could use a clean up pass to close out the
50+ open connections that exist that the end of the test.



git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1450841 13f79535-47bb-0310-9956-ffa450edef68