Closes #62 Upon taking the lead, oracle verifies it can no longer connec...

...t to previous oracle
My thinking was that an Oracle would likely revoke leadership only in the case where the JVM failed or the server was disconnected. You bring up a great point that it's still possible an Oracle got interrupted out of their takeLeadership method even though the JVM is still running- and further, it's possible they have requeued for leadership and the thrift port is still listening.