QPID-6071: [Java Broker] Cause BDB HA to generate ping transaction if local quorum settings are changed

* If user changes the settings used to judge whether quorum is present (that is designated primary in the two node
  case and electable group override in the case of multi node groups), REF now generates a 'ping' transaction allow
  the node to promptly detect too few replicas.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1622844 13f79535-47bb-0310-9956-ffa450edef68