config ang key validation and UT for the same

Change-Id: I507740fc9da3f3da5fb3c88a7414f87db6251c5b
diff --git a/src/test/resources/ListSubStatements.yang b/src/test/resources/ListSubStatements.yang
index f684780..109fc17 100644
--- a/src/test/resources/ListSubStatements.yang
+++ b/src/test/resources/ListSubStatements.yang
@@ -3,7 +3,7 @@
     namespace http://huawei.com;
     prefix Ant;
     list ospf {
-        key "process-id";
+        key "invalid-interval";
         config true;
         max-elements 10;
         min-elements 3;