Registry module is disabled by default so we can still run ONOS without it trying to connect to zookeeper.

Added a config option to enable it. The option is (currently)
net.floodlightcontroller.mastership.MastershipManager.enableZookeeper = true
diff --git a/src/main/java/net/floodlightcontroller/mastership/IMastershipService.java b/src/main/java/net/floodlightcontroller/mastership/IMastershipService.java
index cc0ddf4..bfb2e9a 100644
--- a/src/main/java/net/floodlightcontroller/mastership/IMastershipService.java
+++ b/src/main/java/net/floodlightcontroller/mastership/IMastershipService.java
@@ -32,16 +32,16 @@
 	 * @param controller A string identifying the controller and (possibly) how to talk to it.
 	 * (We will have to develop a convention for this - most likely hostname:port)
 	 */
-	public void registerController(String controllerId) throws Exception;
+	public void registerController(String controllerId) throws RegistryException;
 	
 	/**
 	 * Get all controllers in the cluster
 	 * @return
 	 */
-	public Collection<String> getAllControllers() throws Exception;
+	public Collection<String> getAllControllers() throws RegistryException;
 	
 	
-	public String getControllerForSwitch(long dpid) throws Exception;
+	public String getControllerForSwitch(long dpid) throws RegistryException;
 	
 	public Collection<Long> getSwitchesControlledByController(String controllerId);
 }