fixed success condition check in jsma and added more comments to main function for jsma
fixed success condition check in jsma and added more comments to main function for jsma

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