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

Change-Id: I810aa90636c55c8b05c146780ad28c307cefff33
(cherry picked from commit f31ac6ff9f72d040b2da80b6ee5c630ccf9dcc55)
diff --git a/core/api/src/test/java/org/onosproject/cfg/ComponentConfigAdapter.java b/core/api/src/test/java/org/onosproject/cfg/ComponentConfigAdapter.java
index e0e2acc..97fa037 100644
--- a/core/api/src/test/java/org/onosproject/cfg/ComponentConfigAdapter.java
+++ b/core/api/src/test/java/org/onosproject/cfg/ComponentConfigAdapter.java
@@ -57,4 +57,9 @@
     public void unsetProperty(String componentName, String name) {
 
     }
+
+    @Override
+    public ConfigProperty getProperty(String componentName, String attribute) {
+        return null;
+    }
 }