config ang key validation and UT for the same

Change-Id: I507740fc9da3f3da5fb3c88a7414f87db6251c5b
diff --git a/utils/yangutils/src/test/resources/ModuleSubStatementList.yang b/utils/yangutils/src/test/resources/ModuleSubStatementList.yang
index baf36e7..1bb3bf5 100644
--- a/utils/yangutils/src/test/resources/ModuleSubStatementList.yang
+++ b/utils/yangutils/src/test/resources/ModuleSubStatementList.yang
@@ -3,7 +3,7 @@
     namespace http://huawei.com;
     prefix Ant;
     list valid {
-        key "invalid";
+        key "invalid-interval";
         leaf invalid-interval {
             type "uint16";
             units "seconds";