core: do not "warn" about mundane emergency actions

core: do not "warn" about mundane emergency actions

For example in a container we'd log:
Oct 17 17:01:10 rawhide systemd[1]: Started Power-Off.
Oct 17 17:01:10 rawhide systemd[1]: Forcibly powering off: unit succeeded
Oct 17 17:01:10 rawhide systemd[1]: Reached target Power-Off.
Oct 17 17:01:10 rawhide systemd[1]: Shutting down.
and on the console we'd write (in red)
[  !!  ] Forcibly powering off: unit succeeded

This is not useful in any way, and the fact that we're calling an "emergency action"
is an internal implementation detail. Let's log about c-a-d and the watchdog actions
only.