[Merge] ~cjwatson/livecd-rootfs:bionic/buildd into livecd-rootfs:ubuntu/bionic

[Colin Watson]

@sil2100: Thanks for your comments.  I talked with Adam about this the other day and he agreed, so I've simplified this and the similar xenial change in light of that.
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https://code.launchpad.net/~cjwatson/livecd-rootfs/+git/livecd-rootfs/+merge/361825
Your team Ubuntu Core Development Team is requested to review the proposed merge of ~cjwatson/livecd-rootfs:bionic/buildd into livecd-rootfs:ubuntu/bionic.