virNetDaemonAutoShutdown: Allow live update of shutdown timeout

virNetDaemonAutoShutdown: Allow live update of shutdown timeout

Modify the code so that calling 'virNetDaemonAutoShutdown' will update
the auto shutdown timeout also for running daemons.

This involves changing the logic when to do the update of the timer so
that it can be called from both when the daemon is not yet runnign and
when doing a live update.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>