Use power management functions from ConsoleKit2 if available.
Suspend and hibernate functionality was removed from upower 0.99.0, so systems not using systemd had now suspend/hibernate functionality. Support for this was added into ConsoleKit2.
Most systems will either be systemd or ConsoleKit2 now, so we try the following: 1. Power management in logind 2. Power management in ConsoleKit 3. upower for suspend/resume (really only here to not break backwards compatibility)