[ONOS-6324] Add getOrDefault method to ConsistentMap.

Change-Id: Ice7ad6260c6eb8076320ef469874c0c4ceeadc19
diff --git a/core/api/src/test/java/org/onosproject/store/service/ConsistentMapAdapter.java b/core/api/src/test/java/org/onosproject/store/service/ConsistentMapAdapter.java
index e6e71c2..4494db2 100644
--- a/core/api/src/test/java/org/onosproject/store/service/ConsistentMapAdapter.java
+++ b/core/api/src/test/java/org/onosproject/store/service/ConsistentMapAdapter.java
@@ -64,6 +64,11 @@
     }
 
     @Override
+    public Versioned<V> getOrDefault(K key, V defaultValue) {
+        return null;
+    }
+
+    @Override
     public Versioned<V> computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
         return null;
     }