doc: document that restart command only restarts running services

[Clint Byrum]

This is related to bug #707479 , which has been closed as Won't Fix in upstart.

I think this deserves some mention in the initctl man page, as its somewhat confusing when set next to common sysvinit script practices. Many (most?) traditional sysvinit scripts, upon given restart, do:

restart)
  $0 stop
  $0 start
  ;;

Since upstart has implemented a somewhat less common behavior, this should be noted in the man page.

I would propose adding this to the initctl man page as a new paragraph in the restart sub command:

"The instance of JOB being restarted will keep its running configuration. If the job file has been changed, one would need to stop and then start the job to run with the new job configuration."