[Merge] ~codyshepherd/livecd-rootfs/+git/livecd-rootfs:serialize-systemd-grub into livecd-rootfs:ubuntu/master

[Cody Shepherd]

The proposal to merge ~codyshepherd/livecd-rootfs/+git/livecd-rootfs:serialize-systemd-grub into livecd-rootfs:ubuntu/master has been updated.

Commit message changed to:

Add systemd config to serialize invocations of grub-editenv (temporary workaround for LP: #1910815)

For more details, see:
https://code.launchpad.net/~codyshepherd/livecd-rootfs/+git/livecd-rootfs/+merge/397752
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Your team Ubuntu Core Development Team is requested to review the proposed merge of ~codyshepherd/livecd-rootfs/+git/livecd-rootfs:serialize-systemd-grub into livecd-rootfs:ubuntu/master.