This role now expects disks to be passed as a list instead of a
comma-separated string.
This commit updates group variables to stop transforming disk lists to
comma-separated strings and adds a check for users overriding LVM
variables. The playbook is also tagged as upgrade-check.
Change-Id: Ia8001c28a8be034ae79a1c584beb40bc66891db3
1a3de5e799