Make C lib in `paddle.v2.master.client` lazy load
Make C lib in `paddle.v2.master.client` lazy load

Currently, WITH_GOLANG is a compiling flag, and not all Paddle binary
enable `WITH_GOLANG=ON`. So we cannot ensure that every paddle has
`master.so`. Make load that C libary lazily could let the user run
Paddle without `WITH_GOLANG=ON`.

lispc/Paddle,luotao1/Paddle,luotao1/Paddle,putcn/Paddle,luotao1/Paddle,hedaoyuan/Paddle,chengduoZH/Paddle,hedaoyuan/Paddle,pkuyym/Paddle,pkuyym/Paddle,lcy-seso/Paddle,pengli09/Paddle,tensor-tang/Paddle,pengli09/Paddle,jacquesqiao/Paddle,PaddlePaddle/Paddle,hedaoyuan/Paddle,QiJune/Paddle,pkuyym/Paddle,lispc/Paddle,QiJune/Paddle,yu239/Paddle,reyoung/Paddle,luotao1/Paddle,yu239/Paddle,Canpio/Paddle,jacquesqiao/Paddle,Canpio/Paddle,reyoung/Paddle,lispc/Paddle,yu239/Paddle,Canpio/Paddle,baidu/Paddle,pengli09/Paddle,chengduoZH/Paddle,pkuyym/Paddle,jacquesqiao/Paddle,PaddlePaddle/Paddle,pkuyym/Paddle,luotao1/Paddle,lispc/Paddle,Canpio/Paddle,lispc/Paddle,PaddlePaddle/Paddle,tensor-tang/Paddle,baidu/Paddle,pengli09/Paddle,lcy-seso/Paddle,QiJune/Paddle,QiJune/Paddle,baidu/Paddle,hedaoyuan/Paddle,PaddlePaddle/Paddle,QiJune/Paddle,tensor-tang/Paddle,jacquesqiao/Paddle,tensor-tang/Paddle,pkuyym/Paddle,lispc/Paddle,baidu/Paddle,tensor-tang/Paddle,lispc/Paddle,lispc/Paddle,hedaoyuan/Paddle,reyoung/Paddle,putcn/Paddle,chengduoZH/Paddle,yu239/Paddle,hedaoyuan/Paddle,PaddlePaddle/Paddle,reyoung/Paddle,yu239/Paddle,PaddlePaddle/Paddle,putcn/Paddle,chengduoZH/Paddle,pengli09/Paddle,reyoung/Paddle,Canpio/Paddle,putcn/Paddle,Canpio/Paddle,yu239/Paddle,PaddlePaddle/Paddle,pengli09/Paddle,baidu/Paddle,luotao1/Paddle,pengli09/Paddle,luotao1/Paddle,jacquesqiao/Paddle,yu239/Paddle,pengli09/Paddle,putcn/Paddle,QiJune/Paddle,hedaoyuan/Paddle,lcy-seso/Paddle,Canpio/Paddle,lcy-seso/Paddle,yu239/Paddle,lcy-seso/Paddle,lcy-seso/Paddle,jacquesqiao/Paddle,chengduoZH/Paddle,Canpio/Paddle,putcn/Paddle,hedaoyuan/Paddle,reyoung/Paddle