MastershipManagerTest plus tweaks to MastershipStore

Change-Id: Ie5d3201ce2297ae68cdafac4439168989dd804c5
diff --git a/core/store/src/main/java/org/onlab/onos/store/cluster/impl/DistributedMastershipStore.java b/core/store/src/main/java/org/onlab/onos/store/cluster/impl/DistributedMastershipStore.java
index 92d6880..c15d6aa 100644
--- a/core/store/src/main/java/org/onlab/onos/store/cluster/impl/DistributedMastershipStore.java
+++ b/core/store/src/main/java/org/onlab/onos/store/cluster/impl/DistributedMastershipStore.java
@@ -40,6 +40,7 @@
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected ClusterService clusterService;
 
+    @Override
     @Activate
     public void activate() {
         super.activate();
@@ -59,10 +60,10 @@
     }
 
     @Override
-    public MastershipEvent setRole(NodeId nodeId, DeviceId deviceId, MastershipRole role) {
+    public MastershipEvent setMaster(NodeId nodeId, DeviceId deviceId) {
         synchronized (this) {
             NodeId currentMaster = getMaster(deviceId);
-            if (role == MastershipRole.MASTER && Objects.equals(currentMaster, nodeId)) {
+            if (Objects.equals(currentMaster, nodeId)) {
                 return null;
             }
 
@@ -92,7 +93,7 @@
     @Override
     public MastershipRole requestRole(DeviceId deviceId) {
         // FIXME: for now we are 'selecting' as master whoever asks
-        setRole(clusterService.getLocalNode().id(), deviceId, MastershipRole.MASTER);
+        setMaster(clusterService.getLocalNode().id(), deviceId);
         return MastershipRole.MASTER;
     }