Rebase to tier-1 base images

[p5]

It would be good to rebase ontop of the Tier 1 base images, rather than Tier 0 so we can more closely follow upstream.

This is currently not possible because the Tier 1 images exclude packages such as Perl - a dependency for KDE and various other desktops.

Upstream issue:
coreos/rpm-ostree#5081