Close connection if frpc can't connection to local server
Close connection if frpc can't connection to local server

Now, when frpc can't connect to local server it leaves the connection alone, the patch fix it.

Fixed #575

bingtianbaihua/frp,fatedier/frp,Hurricanezwf/frp,Hurricanezwf/frp,fatedier/frp,Hurricanezwf/frp,bingtianbaihua/frp,fatedier/frp,Hurricanezwf/frp,fatedier/frp,bingtianbaihua/frp,bingtianbaihua/frp