add roleInfo structure and backup_changed mastership event

Change-Id: Iedee219fe250d681377d73a50a71f5fa72cd7802
diff --git a/core/net/src/main/java/org/onlab/onos/cluster/impl/MastershipManager.java b/core/net/src/main/java/org/onlab/onos/cluster/impl/MastershipManager.java
index 7cf14fc..867c6cb 100644
--- a/core/net/src/main/java/org/onlab/onos/cluster/impl/MastershipManager.java
+++ b/core/net/src/main/java/org/onlab/onos/cluster/impl/MastershipManager.java
@@ -228,8 +228,8 @@
                 return true;
             }
             //else {
-                //FIXME: break tie for equal-sized clusters,
-                //       maybe by number of connected switches
+                //FIXME: break tie for equal-sized clusters, by number of
+                //       connected switches, then masters, then nodeId hash
             // }
             return false;
         }