fix data parallel bug

Author: Ze-Yang

segmentation_module.py

@@ -17,7 +17,7 @@
 
 def make_model(opts, classes=None):
     if opts.norm_act == 'iabn_sync':
-        norm = partial(InPlaceABNSync, activation="leaky_relu", activation_param=.01)
+        norm = partial(InPlaceABNSync, activation="leaky_relu", activation_param=.01, group=distributed.group.WORLD)
     elif opts.norm_act == 'iabn':
         norm = partial(InPlaceABN, activation="leaky_relu", activation_param=.01)
     elif opts.norm_act == 'abn':