Fix Bug of mux_redux in ssh-rd

The msftguy's ssh-rd(https://github.com/msftguy/ssh-rd) is a useful tool to make iOS ramdisk. It also contain a module usb-mux, it's independent and can be reuse. But there is a little bug in it.

mux.c. If the device connect failed, the 'local socket' will be blocked. More worst, if you dis-connect and re-connect again, the older 'socket' still blocked and new socket also can't startup(cause of listen(socket, 0)). If it shutdown the accepted socket when Device Connect Failed, the bug was gone.

This is my patch of it.

160c160< int new_sock;---> int new_sock = -1;257a258> if (new_sock > 0) closesocket(new_sock);264a266> if (new_sock > 0) closesocket(new_sock);

I had submit this patch to author. If he refused, hope this could help you.