save infer model bug fix (#16224)

* save infer model bug fix

* test=release/1.3

Author: fc500110

python/paddle/fluid/io.py

@@ -948,10 +948,11 @@ def save_inference_model(dirname,
     # TODO(Superjomn) add an IR pass to remove 1-scale op.
     with program_guard(main_program):
         uniq_target_vars = []
-        for var in target_vars:
+        for i, var in enumerate(target_vars):
             if isinstance(var, Variable):
-                var1 = layers.scale(var, 1.)
-            uniq_target_vars.append(var1)
+                var = layers.scale(
+                    var, 1., name="save_infer_model/scale_{}".format(i))
+            uniq_target_vars.append(var)
         target_vars = uniq_target_vars
 
     # when a pserver and a trainer running on the same machine, mkdir may conflict