parser json FEATURE support for nested ext instances with data

... such as schema-mount.
diff --git a/tests/modules/yang/sm.yang b/tests/modules/yang/sm.yang
index 00e9595..3da9c9a 100644
--- a/tests/modules/yang/sm.yang
+++ b/tests/modules/yang/sm.yang
@@ -22,9 +22,7 @@
             leaf name {
                 type string;
             }
-            container mnt-root {
-                yangmnt:mount-point "mnt-root";
-            }
+            yangmnt:mount-point "mnt-root";
         }
     }
     leaf target {