config ang key validation and UT for the same

Change-Id: I507740fc9da3f3da5fb3c88a7414f87db6251c5b
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/parserutils/ListenerValidation.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/parserutils/ListenerValidation.java
index 226a530..26e4907 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/parserutils/ListenerValidation.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/parserutils/ListenerValidation.java
@@ -16,6 +16,10 @@
 
 package org.onosproject.yangutils.parser.impl.parserutils;
 
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.parser.Parsable;
 import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
@@ -83,4 +87,25 @@
             throw new ParserException(message);
         }
     }
+
+    /**
+     * Returns parent node config value, if top node does not specify a config statement
+     * then default value true is returned.
+     *
+     * @param listener listener's object.
+     * @return true/false parent's config value.
+     */
+    public static boolean getParentNodeConfig(TreeWalkListener listener) {
+        YangNode parentNode;
+        Parsable curData = listener.getParsedDataStack().peek();
+        if (curData instanceof YangNode) {
+            parentNode = ((YangNode) curData).getParent();
+            if (parentNode instanceof YangContainer) {
+                return ((YangContainer) parentNode).isConfig();
+            } else if (parentNode instanceof YangList) {
+                return ((YangList) parentNode).isConfig();
+            }
+        }
+        return true;
+    }
 }