list mastership roles CLI command

Change-Id: I54dc296f90c4b8ceebe4e86816c3796da4d2d714
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 59614da..4bcaff4a 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
@@ -3,6 +3,7 @@
 import static com.google.common.base.Preconditions.checkNotNull;
 import static org.slf4j.LoggerFactory.getLogger;
 
+import java.util.List;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -127,6 +128,11 @@
         return store.getDevices(nodeId);
     }
 
+    @Override
+    public List<NodeId> getNodesFor(DeviceId deviceId) {
+        checkNotNull(deviceId, DEVICE_ID_NULL);
+        return store.getNodes(deviceId);
+    }
 
     @Override
     public MastershipTermService requestTermService() {