core: Preventing moving a shareable disk to a Gluster domain

Gluster domian does not support shareable disks- therefor
MoveDisksCommand now prevents this action. Tests are also added.

Change-Id: I37e500e86d2b6094bb257221a4ca899590aed610
Bug-Url: https://bugzilla.redhat.com/1135771
Signed-off-by: Amit Aviram <aaviram@redhat.com>