The approach here is to use the availability zone as an imaginary rack.
All hosts that are in the same AZ will be in the same imaginary rack.
From Ceph's perspective this doesn't matter as it's just a bucket after all.
This will give users the ability to further customize their ceph deployment.
Change-Id: Ie25ac1b001db558d6a40fe3eaca014e8f4174241
* Select least-used journal disk instead of blind RR
* Add safeguard for OSD journals
* Avoid zapping journals repeatedly, add check for journal partition type
* Check that journal devices don't overlap with data devices