logind: print what action is ignored

My logs have lines like this:
Oct 10 09:38:38 krowka systemd-logind[1889]: External (2) displays connected.
Oct 10 09:38:38 krowka systemd-logind[1889]: Refusing operation, as it is turned off.
Without some hint *what* operation is ignored, this is not very informative.

(I remember this came up before, but I don't remember why we didn't change this
log line back then...)

(cherry picked from commit bf135d82)