Add profile.sh script for multi-gpu profiling for DS2.
Created by: xinghai-sun
Provide a script doing experiments in https://github.com/PaddlePaddle/Paddle/issues/3137#issuecomment-320996396
Created by: xinghai-sun
Provide a script doing experiments in https://github.com/PaddlePaddle/Paddle/issues/3137#issuecomment-320996396