[Merge] ~jibel/livecd-rootfs/+git/add_multi_layered_squashfses_support:ubuntu/master into livecd-rootfs:ubuntu/master

[Jean-Baptiste Lallement]

Fixes pushed and branched rebased on ubuntu/master.
-- 
https://code.launchpad.net/~jibel/livecd-rootfs/+git/add_multi_layered_squashfses_support/+merge/360878
Your team Ubuntu Core Development Team is subscribed to branch livecd-rootfs:ubuntu/master.