[Merge] ~chad.smith/livecd-rootfs:cloud-init-nm-in-override into livecd-rootfs:ubuntu/master

[Chad Smith]

This avoids debsums issues and also avoids full replacement of the entire cloud-init.service file introduced to fix https://bugs.launchpad.net/bugs/2008952 
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https://code.launchpad.net/~chad.smith/livecd-rootfs/+git/livecd-rootfs/+merge/469479
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