Add the ability to force-kill a service if it does not go down
successfully. Also, adjust the default wait time for an s6 service to go
down to 60 seconds.
This changes the default s6 service directory to /var/svc.d, also
it changes the code to work with the individual services instead of
forcing a rescan when a service is started or stopped.
William Hubbs
Jakub Jirutka
Mike Frysinger