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

[Dan Bungert]

> Clearly neither approach guards against a renamed service. It would be nice to have a check for that as well (if the main unit file doesn't exist, abort)

I'm assuming this bit is non-blocking.

Uploading.
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https://code.launchpad.net/~chad.smith/livecd-rootfs/+git/livecd-rootfs/+merge/473594
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