fix acc diff problem caused by pr #44116 (#44311)

python/paddle/fluid/contrib/slim/quantization/quantization_pass.py

@@ -1440,11 +1440,18 @@ class OutScaleForTrainingPass(object):
                         [core.VarDesc.VarType.FP64, core.VarDesc.VarType.FP32]:
                         continue
 
+                    try:
+                        graph._find_node_by_name(
+                            graph.all_var_nodes(),
+                            self._scale_name(in_node.name()))
+                        continue
+                    except:
                         scale_node = graph.create_persistable_node(
                             name=self._scale_name(in_node.name()),
                             var_type=core.VarDesc.VarType.LOD_TENSOR,
                             shape=[1],
                             var_dtype=in_node.dtype())
+
                     data_type = 'float64' if in_node.dtype() \
                         == core.VarDesc.VarType.FP64 else 'float32'
                     _init_var_node(scale_node, np.ones([1], dtype=data_type),