QPID-5991: [Java System Tests]  BDB HA System Test Improvements

* Change failover url so that algorithm for cases where we expect a connection to the broker checks each broker once
  per cycle rather than twice successively.  Doubled the number of cycles and reduced the connect delay so that
  test discover the master node more quickly.
* Use separate negative failover url when expectation is that group will refuse connection.
* Remove duplicated test
* In TwoNodeTest use REST API only.   JMXManagementTest now has sole responsibility for testing HA using the JMX bean.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1617895 13f79535-47bb-0310-9956-ffa450edef68