[ONOS-4762][ONOS-4601]Grammar for meta data +  Union defect fix

Change-Id: I8f78127e5b292cca6a79b32d496c2602c9105acd
diff --git a/plugin/src/test/resources/UnionWithoutChild.yang b/plugin/src/test/resources/UnionWithoutChild.yang
new file mode 100644
index 0000000..14d3329
--- /dev/null
+++ b/plugin/src/test/resources/UnionWithoutChild.yang
@@ -0,0 +1,14 @@
+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    list valid {
+        key "invalid-interval";
+        leaf invalid-interval {
+            type union {
+               type "union";
+            }
+        }
+    }
+}
+