Added one more Component Config REST API; for specified component and variable.

Change-Id: I810aa90636c55c8b05c146780ad28c307cefff33
diff --git a/incubator/protobuf/services/nb/src/test/java/org/onosproject/incubator/protobuf/services/nb/GrpcNbComponentConfigServiceTest.java b/incubator/protobuf/services/nb/src/test/java/org/onosproject/incubator/protobuf/services/nb/GrpcNbComponentConfigServiceTest.java
index 011de5a..2b6021c 100644
--- a/incubator/protobuf/services/nb/src/test/java/org/onosproject/incubator/protobuf/services/nb/GrpcNbComponentConfigServiceTest.java
+++ b/incubator/protobuf/services/nb/src/test/java/org/onosproject/incubator/protobuf/services/nb/GrpcNbComponentConfigServiceTest.java
@@ -273,5 +273,10 @@
         public void unsetProperty(String componentName, String name) {
             STRING_MAP2.remove(componentName + "#" + name);
         }
+
+        @Override
+        public ConfigProperty getProperty(String componentName, String attribute) {
+            return null;
+        }
     }
 }