[ONOS-4460] Relinquish device role when partitioned away from cluster

Change-Id: I578029614cced96a2d4503e4fe3052c927f051ab
diff --git a/core/api/src/main/java/org/onosproject/mastership/MastershipEvent.java b/core/api/src/main/java/org/onosproject/mastership/MastershipEvent.java
index 1d3bbfd..1156787 100644
--- a/core/api/src/main/java/org/onosproject/mastership/MastershipEvent.java
+++ b/core/api/src/main/java/org/onosproject/mastership/MastershipEvent.java
@@ -44,7 +44,13 @@
          * the change in the backups list is accompanied by a change in
          * master, the event is subsumed by MASTER_CHANGED.
          */
-        BACKUPS_CHANGED
+        BACKUPS_CHANGED,
+
+        /**
+         * Signifies that the underlying storage for the Mastership state
+         * of this device is unavailable.
+         */
+        SUSPENDED
     }
 
     /**