[Merge] ~seb128/livecd-rootfs:restore-desktop-minimal into livecd-rootfs:ubuntu/master

[Sebastien Bacher]

We will also need to revert https://git.launchpad.net/~ubuntu-cdimage/debian-cd/+git/ubuntu/commit/?id=a7deff52
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https://code.launchpad.net/~seb128/livecd-rootfs/+git/livecd-rootfs/+merge/451164
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