Publishing connection info for active master (e.g. HBase Active Master)

Some applications, such as HBase, may have multiple masters with one active at any given point. When such applications register the applied configuration or the access URL for UI/JMX etc. then the url registered or the ports advertised should belong to the active master.

Slider should support a way to have the application indicate which master is active and what information must be registered by the active master. Related effort is to refresh the registry when failover occurs.