[Merge] livecd-rootfs:u-i-disk-info into livecd-rootfs:ubuntu/master

[Łukasz Zemczak]

Cherry-picking the same change for bionic. Will release this for focal once we have the new ubuntu-image in there.
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https://code.launchpad.net/~ubuntu-core-dev/livecd-rootfs/+git/livecd-rootfs/+merge/376790
Your team Ubuntu Core Development Team is requested to review the proposed merge of livecd-rootfs:u-i-disk-info into livecd-rootfs:ubuntu/master.