tests: Run tests on /tmp (not /var/tmp)
tests: Run tests on /tmp (not /var/tmp)

Since we now are ok with no-xattrs this means we can run on tmpfs.

Closes: #1839
Approved by: alexlarsson

flatpak/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,flatpak/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,flatpak/flatpak