fix reid resnet bn export (#5168)

ppdet/modeling/reid/resnet.py

@@ -55,12 +55,14 @@ class ConvBNLayer(nn.Layer):
             bias_attr=False,
             data_format=data_format)
 
-        self._batch_norm = nn.BatchNorm(
-            num_filters, act=act, data_layout=data_format)
+        self._batch_norm = nn.BatchNorm2D(num_filters)
+        self.act = act
 
     def forward(self, inputs):
         y = self._conv(inputs)
         y = self._batch_norm(y)
+        if self.act:
+            y = getattr(F, self.act)(y)
         return y