Favor adapter classes over service interfaces in unit tests

In unit tests that are mocking an entire interface, instead
extend the Adapter class so the unused method overrides
are no longer needed.

Change-Id: I6e332cc5cb59410f163deea223fbc94e73d83917
diff --git a/core/net/src/test/java/org/onosproject/cluster/impl/MastershipManagerTest.java b/core/net/src/test/java/org/onosproject/cluster/impl/MastershipManagerTest.java
index dfde09f..52ee04f 100644
--- a/core/net/src/test/java/org/onosproject/cluster/impl/MastershipManagerTest.java
+++ b/core/net/src/test/java/org/onosproject/cluster/impl/MastershipManagerTest.java
@@ -20,10 +20,10 @@
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
-import org.onosproject.cluster.ClusterEventListener;
+import org.onlab.packet.IpAddress;
 import org.onosproject.cluster.ClusterService;
+import org.onosproject.cluster.ClusterServiceAdapter;
 import org.onosproject.cluster.ControllerNode;
-import org.onosproject.cluster.ControllerNode.State;
 import org.onosproject.cluster.DefaultControllerNode;
 import org.onosproject.cluster.NodeId;
 import org.onosproject.event.impl.TestEventDispatcher;
@@ -32,13 +32,14 @@
 import org.onosproject.mastership.MastershipTermService;
 import org.onosproject.net.DeviceId;
 import org.onosproject.store.trivial.impl.SimpleMastershipStore;
-import org.onlab.packet.IpAddress;
 
 import com.google.common.collect.Sets;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNull;
-import static org.onosproject.net.MastershipRole.*;
+import static org.onosproject.net.MastershipRole.MASTER;
+import static org.onosproject.net.MastershipRole.NONE;
+import static org.onosproject.net.MastershipRole.STANDBY;
 
 /**
  * Test codifying the mastership service contracts.
@@ -151,7 +152,7 @@
         assertEquals("inconsistent terms: ", 3, ts.getMastershipTerm(DEV_MASTER).termNumber());
     }
 
-    private final class TestClusterService implements ClusterService {
+    private final class TestClusterService extends ClusterServiceAdapter {
 
         ControllerNode local = new DefaultControllerNode(NID_LOCAL, LOCALHOST);
 
@@ -165,24 +166,6 @@
             return Sets.newHashSet();
         }
 
-        @Override
-        public ControllerNode getNode(NodeId nodeId) {
-            return null;
-        }
-
-        @Override
-        public State getState(NodeId nodeId) {
-            return null;
-        }
-
-        @Override
-        public void addListener(ClusterEventListener listener) {
-        }
-
-        @Override
-        public void removeListener(ClusterEventListener listener) {
-        }
-
     }
 
     private final class TestSimpleMastershipStore extends SimpleMastershipStore