!14691 fix fastrcnn error for pynative

From: @chujinjin
Reviewed-by: @jjfeing,@kisnwang
Signed-off-by: @kisnwang

mindspore/ops/operations/array_ops.py

@@ -321,6 +321,8 @@ class Cast(PrimitiveWithInfer):
     def check_elim(self, x, dtype):
         if isinstance(x, (Tensor, numbers.Number, Parameter)):
             if isinstance(x, Tensor) and x.dtype == dtype:
+                x = Tensor(x)
+                x.set_cast_dtype()
                 return (True, x)
             if isinstance(x, numbers.Number):
                 return (True, Tensor(x, dtype=dtype))

model_zoo/official/cv/faster_rcnn/src/FasterRcnn/rcnn.py

@@ -143,7 +143,7 @@ class Rcnn(nn.Cell):
 
         if self.training:
             bbox_weights = self.cast(self.logicaland(self.greater(labels, 0), mask), mstype.int32) * labels
-            labels = self.cast(self.onehot(labels, self.num_classes, self.on_value, self.off_value), self.ms_type)
+            labels = self.onehot(labels, self.num_classes, self.on_value, self.off_value)
             bbox_targets = self.tile(self.expandims(bbox_targets, 1), (1, self.num_classes, 1))
 
             loss, loss_cls, loss_reg, loss_print = self.loss(x_cls, x_reg, bbox_targets, bbox_weights, labels, mask)