gtkapplication-quartz: clean up inhibit code
gtkapplication-quartz: clean up inhibit code

When testing with bloatpad, the existing inhibit code seems not to be
working at all.  Replace it with a cleaner and simpler version that
works.

https://bugzilla.gnome.org/show_bug.cgi?id=720551

jigpu/gtk,jadahl/gtk,jessevdk/gtk,ahodesuka/gtk,ahodesuka/gtk,Lyude/gtk-,Lyude/gtk-,Lyude/gtk-,davidgumberg/gtk,davidgumberg/gtk,davidgumberg/gtk,jigpu/gtk,jigpu/gtk,Lyude/gtk-,alexlarsson/gtk,chergert/gtk,grubersjoe/adwaita,jessevdk/gtk,chergert/gtk,Sidnioulz/SandboxGtk,jessevdk/gtk,davidgumberg/gtk,alexlarsson/gtk,Adamovskiy/gtk,Adamovskiy/gtk,Adamovskiy/gtk,Adamovskiy/gtk,grubersjoe/adwaita,jigpu/gtk,jadahl/gtk,Adamovskiy/gtk,ahodesuka/gtk,alexlarsson/gtk,jadahl/gtk,chergert/gtk,alexlarsson/gtk,jigpu/gtk,jadahl/gtk,jadahl/gtk,Adamovskiy/gtk,grubersjoe/adwaita,davidgumberg/gtk,davidgumberg/gtk,msteinert/gtk,Lyude/gtk-,jadahl/gtk,Adamovskiy/gtk,grubersjoe/adwaita,jadahl/gtk,ahodesuka/gtk,Lyude/gtk-,chergert/gtk,Sidnioulz/SandboxGtk,davidgumberg/gtk,alexlarsson/gtk,chergert/gtk,ahodesuka/gtk,Lyude/gtk-,jigpu/gtk,msteinert/gtk,chergert/gtk,msteinert/gtk,jigpu/gtk,jadahl/gtk,jessevdk/gtk,msteinert/gtk,ahodesuka/gtk,alexlarsson/gtk,chergert/gtk,Sidnioulz/SandboxGtk,Adamovskiy/gtk,davidgumberg/gtk,ahodesuka/gtk,msteinert/gtk,grubersjoe/adwaita,alexlarsson/gtk,jessevdk/gtk,Sidnioulz/SandboxGtk,chergert/gtk,grubersjoe/adwaita,alexlarsson/gtk,jigpu/gtk,Lyude/gtk-,jessevdk/gtk,grubersjoe/adwaita,ahodesuka/gtk,jessevdk/gtk,Sidnioulz/SandboxGtk,Sidnioulz/SandboxGtk,grubersjoe/adwaita,msteinert/gtk