symbol_darknet19.py batchnorm layers use_global_stats problems

Hi,

in symbol/symbol_darknet19.py,there is some batchnorm layers  
and I notice that use_global_stats should be True when demo or inference.
But in the demo.py I didn't see use_global_stats set to be True. Did I make a mistake?
thanks.

`conv = mx.symbol.BatchNorm(data=conv, name="bn_{}".format(name))`