!13355 add degree and mean to TrainOneStepCell

From: @wangnan39
Reviewed-by: @kingxian,@zh_qh
Signed-off-by: @kingxian

mindspore/nn/wrap/cell_wrapper.py

@@ -349,9 +349,9 @@ class TrainOneStepCell(Cell):
         if self.parallel_mode in (ParallelMode.DATA_PARALLEL, ParallelMode.HYBRID_PARALLEL):
             self.reducer_flag = True
         if self.reducer_flag:
-            mean = _get_gradients_mean()
-            degree = _get_device_num()
-            self.grad_reducer = DistributedGradReducer(self.weights, mean, degree)
+            self.mean = _get_gradients_mean()
+            self.degree = _get_device_num()
+            self.grad_reducer = DistributedGradReducer(self.weights, self.mean, self.degree)
 
     def construct(self, *inputs):
         weights = self.weights