Revert "Add ubuntu user to docker group"
Revert "Add ubuntu user to docker group"

Don't do this here, use cloud-init

This reverts commit 6dc5a43e5467f8367cd0d55cbff4d76d601fbb12.

Change-Id: Ie237a63eb33e69f8f2cc354ae061d105ecef15f6

NeCTAR-RC/nectar-images,NeCTAR-RC/nectar-images