fix bug where set_input_shape was called in MLP's init and layer variable could not be realized by keys before and after a new call.
fix bug where set_input_shape was called in MLP's init and layer variable could not be realized by keys before and after a new call.

carlini/cleverhans,carlini/cleverhans,cleverhans-lab/cleverhans,cleverhans-lab/cleverhans,openai/cleverhans,cleverhans-lab/cleverhans,cihangxie/cleverhans