MastershipManagerTest plus tweaks to MastershipStore

Change-Id: Ie5d3201ce2297ae68cdafac4439168989dd804c5
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 4ac6052..255830c 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
@@ -64,9 +64,12 @@
         checkNotNull(nodeId, NODE_ID_NULL);
         checkNotNull(deviceId, DEVICE_ID_NULL);
         checkNotNull(role, ROLE_NULL);
-        MastershipEvent event = store.setRole(nodeId, deviceId, role);
-        if (event != null) {
-            post(event);
+        //TODO figure out appropriate action for non-MASTER roles, if we even set those
+        if (role.equals(MastershipRole.MASTER)) {
+            MastershipEvent event = store.setMaster(nodeId, deviceId);
+            if (event != null) {
+                post(event);
+            }
         }
     }