sp: fix storage domain link detection

It seems that the storage domain link detection never worked. This patch
fixes the intended behavior.

Related-To: https://bugzilla.redhat.com/show_bug.cgi?id=1116585
Change-Id: I37b44ac15f24be1271334e15ef47fc8316f259eb
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/30245
Reviewed-by: Nir Soffer <nsoffer@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>