Allow user to set SUID on vopono binary, and then don't prompt for sudo, etc.

Most existing code should already work, this is more of a packaging problem. May need minor changes for getting original user ID - see https://github.com/Intika-Linux-Namespace/Netns-Exec/blob/master/netns-exec.c

Also consider using capabilities: https://linux.die.net/man/7/capabilities - if any applicable, e.g. CAP_NET_ADMIN