[Merge] ~mwhudson/livecd-rootfs/+git/livecd-rootfs:layer-fixes into livecd-rootfs:ubuntu/master

[Michael Hudson-Doyle]

So after a bit of a fight to reproduce this, it seems the -- or at least a -- problem is that every layer gets its own initrd. That's not very useful! It's also not super surprising that I didn't see this working on the server image because those don't have a kernel in any published layer. Let's see how to fix this...
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https://code.launchpad.net/~mwhudson/livecd-rootfs/+git/livecd-rootfs/+merge/404721
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