core: Check if data center version supports import data domain upon attach

When we are selecting a data center that does not support import of data
domains, make those options unselectable

Change-Id: I05b6a8fe737691655dedbfbbb8d1f0ee4a592668
Bug-Url: https://bugzilla.redhat.com/1176436
Signed-off-by: Tal Nisan <tnisan@redhat.com>