xfce4-power-manager unable to perform some of it operations due default
systemd/logind settings.
Example: if power-button is set up to 'suspend' and default logind.conf is
commented #HandlePowerKey=, than computer will shutdown if power-button
pressed, ignoring xfce4-power-manager settings.
If logind settings is changed to HandlePowerKey=ignore, all works fine.
This is not xfce4-power-manager problem, but I think it should at least show
warning about incompatible settings in systemd. Systemd gonna be default init
service in future debian version so that problem gonna hit many users. And it
really hard to debug.