[Merge] ~xnox/livecd-rootfs:snap-preseed-with-channel into livecd-rootfs:ubuntu/master

[Stéphane Graber]

Approach looks fine to me for the channel/track syntax. This will cover LXD's needs.
-- 
https://code.launchpad.net/~xnox/livecd-rootfs/+git/livecd-rootfs/+merge/385064
Your team Ubuntu Core Development Team is requested to review the proposed merge of ~xnox/livecd-rootfs:snap-preseed-with-channel into livecd-rootfs:ubuntu/master.