Partially revert f1df5cb to fix --persist
Partially revert f1df5cb to fix --persist

We should not check if a persistence target exists outside of the
chroot, since its existance is irrelevant.

Fixes #1088

Closes: #1089
Approved by: alexlarsson

handsome-feng/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,handsome-feng/flatpak,flatpak/flatpak,handsome-feng/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,handsome-feng/flatpak,matthiasclasen/flatpak,flatpak/flatpak,handsome-feng/flatpak,matthiasclasen/flatpak