ONOS-3552 Do not return group information when a device is unavailable

Change-Id: I84753bf95c47bbebb3156474c03c2860c51ecb4e
diff --git a/core/store/dist/src/test/java/org/onosproject/store/group/impl/DistributedGroupStoreTest.java b/core/store/dist/src/test/java/org/onosproject/store/group/impl/DistributedGroupStoreTest.java
index 560fdb3..dbb63b2 100644
--- a/core/store/dist/src/test/java/org/onosproject/store/group/impl/DistributedGroupStoreTest.java
+++ b/core/store/dist/src/test/java/org/onosproject/store/group/impl/DistributedGroupStoreTest.java
@@ -23,6 +23,7 @@
 import org.junit.Before;
 import org.junit.Test;
 import org.onlab.junit.TestUtils;
+import org.onosproject.cluster.NodeId;
 import org.onosproject.core.DefaultGroupId;
 import org.onosproject.core.GroupId;
 import org.onosproject.mastership.MastershipServiceAdapter;
@@ -106,6 +107,11 @@
         public MastershipRole getLocalRole(DeviceId deviceId) {
             return MastershipRole.MASTER;
         }
+
+        @Override
+        public NodeId getMasterFor(DeviceId deviceId) {
+            return new NodeId("foo");
+        }
     }
 
     @Before