[Merge] ~ikapelyukhin/livecd-rootfs/+git/livecd-rootfs:master-split-disk-image into livecd-rootfs:ubuntu/master

[John Chittum]

Review: Approve

Approve from a CPC perspective. We are moving to separate hooks for more parallelized building, as well as having aggregates available. 
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https://code.launchpad.net/~ikapelyukhin/livecd-rootfs/+git/livecd-rootfs/+merge/415894
Your team Ubuntu Core Development Team is requested to review the proposed merge of ~ikapelyukhin/livecd-rootfs/+git/livecd-rootfs:master-split-disk-image into livecd-rootfs:ubuntu/master.