Addded missing javadoc

Change-Id: I97b263dcefb865b32d9cfa50e83d340f7026a3df
diff --git a/core/api/src/main/java/org/onlab/onos/cluster/MastershipService.java b/core/api/src/main/java/org/onlab/onos/cluster/MastershipService.java
index d417516..b05aa62 100644
--- a/core/api/src/main/java/org/onlab/onos/cluster/MastershipService.java
+++ b/core/api/src/main/java/org/onlab/onos/cluster/MastershipService.java
@@ -17,6 +17,7 @@
      * Returns the role of the local node for the specified device, without
      * triggering master selection.
      *
+     * @param deviceId the the identifier of the device
      * @return role of the current node
      */
     MastershipRole getLocalRole(DeviceId deviceId);