[ONOS-6324] Add getOrDefault method to ConsistentMap.

Change-Id: Ice7ad6260c6eb8076320ef469874c0c4ceeadc19
diff --git a/core/api/src/test/java/org/onosproject/store/service/AsyncConsistentMapAdapter.java b/core/api/src/test/java/org/onosproject/store/service/AsyncConsistentMapAdapter.java
index 4013458..c9161a3 100644
--- a/core/api/src/test/java/org/onosproject/store/service/AsyncConsistentMapAdapter.java
+++ b/core/api/src/test/java/org/onosproject/store/service/AsyncConsistentMapAdapter.java
@@ -56,6 +56,11 @@
     }
 
     @Override
+    public CompletableFuture<Versioned<V>> getOrDefault(K key, V defaultValue) {
+        return null;
+    }
+
+    @Override
     public CompletableFuture<Versioned<V>>
     computeIf(K key, Predicate<? super V> condition,
               BiFunction<? super K, ? super V, ? extends V> remappingFunction) {