overwrite/merge not remove prev inventory data

lib/ansible/inventory/__init__.py

@@ -736,11 +736,11 @@ class Inventory(object):
             if group and host is None:
                 # load vars in dir/group_vars/name_of_group
                 base_path = os.path.realpath(os.path.join(basedir, "group_vars/%s" % group.name))
-                results = self._variable_manager.add_group_vars_file(base_path, self._loader)
+                results = combine_vars(results, self._variable_manager.add_group_vars_file(base_path, self._loader))
             elif host and group is None:
                 # same for hostvars in dir/host_vars/name_of_host
                 base_path = os.path.realpath(os.path.join(basedir, "host_vars/%s" % host.name))
-                results = self._variable_manager.add_host_vars_file(base_path, self._loader)
+                results = combine_vars(results, self._variable_manager.add_host_vars_file(base_path, self._loader))
 
         # all done, results is a dictionary of variables for this particular host.
         return results