!13633 add fix fcn8s

From: @wukesong
Reviewed-by: @liangchenghui,@c_34
Signed-off-by: @liangchenghui

model_zoo/official/cv/FCN8s/train.py

@@ -46,6 +46,8 @@ def train():
     args = parse_args()
     cfg = FCN8s_VOC2012_cfg
     device_num = int(os.environ.get("DEVICE_NUM", 1))
+    context.set_context(mode=context.GRAPH_MODE, enable_auto_mixed_precision=True, save_graphs=False,
+                        device_target="Ascend", device_id=args.device_id)
     # init multicards training
     if device_num > 1:
         parallel_mode = ParallelMode.DATA_PARALLEL
@@ -54,9 +56,6 @@ def train():
     args.rank = get_rank()
     args.group_size = get_group_size()
 
-    context.set_context(mode=context.GRAPH_MODE, enable_auto_mixed_precision=True, save_graphs=False,
-                        device_target="Ascend", device_id=args.device_id)
-
     # dataset
     dataset = data_generator.SegDataset(image_mean=cfg.image_mean,
                                         image_std=cfg.image_std,