hidden slice_vars in distribute transpile, hidden it to users

python/paddle/fluid/io.py

@@ -401,13 +401,12 @@ def load_vars(executor,
                 inputs={},
                 outputs={"Out": load_var_list},
                 attrs={'file_path': os.path.join(dirname, filename)})
-
-        if main_program._slice_vars_and_atts:
-            _load_slice_up_vars(executor, dirname,
-                                main_program._slice_vars_and_atts)
-
         executor.run(load_prog)
 
+        # load slice vars on pserver, if have it.
+        _load_slice_up_vars(executor, dirname,
+                            main_program._slice_vars_and_atts)
+
 
 def load_params(executor, dirname, main_program=None, filename=None):
     """