Fix destroy error in test_ProtoServer.
Fix destroy error in test_ProtoServer.

gangliao/Paddle,PaddlePaddle/Paddle,gangliao/Paddle,tensor-tang/Paddle,cxysteven/Paddle,cxysteven/Paddle,QiJune/Paddle,chengduoZH/Paddle,pengli09/Paddle,chengduoZH/Paddle,emailweixu/Paddle,Canpio/Paddle,QiJune/Paddle,PaddlePaddle/Paddle,livc/Paddle,chengduoZH/Paddle,yu239/Paddle,pengli09/Paddle,jacquesqiao/Paddle,Canpio/Paddle,jacquesqiao/Paddle,putcn/Paddle,pkuyym/Paddle,putcn/Paddle,putcn/Paddle,jacquesqiao/Paddle,lcy-seso/Paddle,lispc/Paddle,yu239/Paddle,pkuyym/Paddle,livc/Paddle,putcn/Paddle,wen-bo-yang/Paddle,PaddlePaddle/Paddle,emailweixu/Paddle,baidu/Paddle,luotao1/Paddle,gangliao/Paddle,PaddlePaddle/Paddle,tensor-tang/Paddle,emailweixu/Paddle,pengli09/Paddle,chengduoZH/Paddle,Canpio/Paddle,jacquesqiao/Paddle,gangliao/Paddle,QiJune/Paddle,pengli09/Paddle,pkuyym/Paddle,yu239/Paddle,emailweixu/Paddle,lcy-seso/Paddle,tensor-tang/Paddle,Canpio/Paddle,lcy-seso/Paddle,hedaoyuan/Paddle,wen-bo-yang/Paddle,hedaoyuan/Paddle,pengli09/Paddle,pengli09/Paddle,pkuyym/Paddle,baidu/Paddle,wen-bo-yang/Paddle,luotao1/Paddle,PaddlePaddle/Paddle,hedaoyuan/Paddle,yu239/Paddle,yu239/Paddle,putcn/Paddle,yu239/Paddle,putcn/Paddle,chengduoZH/Paddle,luotao1/Paddle,jacquesqiao/Paddle,livc/Paddle,reyoung/Paddle,lcy-seso/Paddle,QiJune/Paddle,hedaoyuan/Paddle,pengli09/Paddle,lispc/Paddle,cxysteven/Paddle,lispc/Paddle,tensor-tang/Paddle,wen-bo-yang/Paddle,cxysteven/Paddle,luotao1/Paddle,livc/Paddle,lispc/Paddle,Canpio/Paddle,baidu/Paddle,reyoung/Paddle,gangliao/Paddle,lispc/Paddle,lispc/Paddle,livc/Paddle,emailweixu/Paddle,luotao1/Paddle,reyoung/Paddle,livc/Paddle,yu239/Paddle,jacquesqiao/Paddle,baidu/Paddle,baidu/Paddle,wen-bo-yang/Paddle,QiJune/Paddle,reyoung/Paddle,PaddlePaddle/Paddle,emailweixu/Paddle,reyoung/Paddle,lcy-seso/Paddle,hedaoyuan/Paddle,cxysteven/Paddle,Canpio/Paddle,hedaoyuan/Paddle,cxysteven/Paddle,wen-bo-yang/Paddle,emailweixu/Paddle,livc/Paddle,reyoung/Paddle,Canpio/Paddle,wen-bo-yang/Paddle,cxysteven/Paddle,hedaoyuan/Paddle,QiJune/Paddle,luotao1/Paddle,yu239/Paddle,hedaoyuan/Paddle,gangliao/Paddle,luotao1/Paddle,PaddlePaddle/Paddle,lispc/Paddle,pkuyym/Paddle,gangliao/Paddle,pengli09/Paddle,pkuyym/Paddle,Canpio/Paddle,lispc/Paddle,tensor-tang/Paddle,lcy-seso/Paddle