Add check for unallocated space on controller

Added check for presence of unallocated disk space
on controller node in case Ceph for image storage
is used. All disks on controller should be
allocated for Base System space.

Change-Id: I1471c1997fafd721cb95d8e9d0ba3934a48a4ad7
Closes-bug: #1297364
Merge "Add check for unallocated space on controller"