Switch cobbler to coi::profiles::cobbler_server

This change lets us use coi::profiles::cobbler_server instead
of the cobbler class, which makes it easier to hiera-ize data.
(cherry picked from commit a685c02893da14e2f0fb1e1dcc334887b05f7f47)
Move disk paritioning options to user.common.yaml

Since we're now using the cobbler_server profile from coi,
we should move this data accordingly.
(cherry picked from commit 0d9b22a9441afe1f976b58c8cdcfedc390f523b3)