Fix nonkeyword after keyword bug (#912)

tools/export_serving_model.py

@@ -53,9 +53,9 @@ def save_serving_model(FLAGS, exe, feed_vars, test_fetches, infer_prog):
     serving_io.save_model(
         client_config_folder=serving_client,
         server_model_folder=serving_server,
-        feed_dict,
-        fetch_dict,
-        infer_prog)
+        feed_var_dict=feed_dict,
+        fetch_var_dict=fetch_dict,
+        main_program=infer_prog)
 
 
 def main():