[Merge] ~waveform/livecd-rootfs:prepare-package into livecd-rootfs:ubuntu/master

[Dave Jones]

This particular merge is no longer required as the code for generating the pre-installed desktop images got stripped out of livecd-rootfs anyway.
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https://code.launchpad.net/~waveform/livecd-rootfs/+git/livecd-rootfs/+merge/452563
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