[Merge] ~vorlon/livecd-rootfs:raspi-only-arm64 into livecd-rootfs:ubuntu/master

[Paul Mars]

I understand that now there is no specific case for the raspi2 (and cm3) subarch anywhere in livecd-rootfs. So is there somewhere else, outside of livecd-rootfs, where it should also be cleaned?

And should this be mentioned in the change?  
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https://code.launchpad.net/~vorlon/livecd-rootfs/+git/livecd-rootfs/+merge/457202
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