[MA][diff_privacy][Func] the dpoptimizer run failed and show obj must set_grad

https://gitee.com/mindspore/dashboard?issue_id=I1JXSM
[MA][diff_privacy][Func] Test Cases Fail Because the MindArmour Version Not Match
https://gitee.com/mindspore/dashboard?issue_id=I1KQK5

mindarmour/diff_privacy/train/model.py

@@ -303,6 +303,7 @@ class _TrainOneStepWithLossScaleCell(Cell):
     def __init__(self, network, optimizer, scale_update_cell=None, micro_batches=None, l2_norm_clip=1.0, mech=None):
         super(_TrainOneStepWithLossScaleCell, self).__init__(auto_prefix=False)
         self.network = network
+        self.network.set_grad()
         self.network.add_flags(defer_inline=True)
         self.weights = ParameterTuple(network.trainable_params())
         self.optimizer = optimizer
@@ -450,6 +451,7 @@ class _TrainOneStepCell(Cell):
     def __init__(self, network, optimizer, sens=1.0, micro_batches=None, l2_norm_clip=1.0, mech=None):
         super(_TrainOneStepCell, self).__init__(auto_prefix=False)
         self.network = network
+        self.network.set_grad()
         self.network.add_flags(defer_inline=True)
         self.weights = optimizer.parameters
         self.optimizer = optimizer