Allow moving of sparse images to a block domains

When attempting to move a sparse image from a file domain to a block domain
the destination image is created as sparse which is not supported on block
domains.
This patch allows to create the images preallocated on domains that do not
support sparseness

Change-Id: Id95d700cf6acb46464d6c5d063966f9331a15028
Signed-off-by: Tal Nisan <tnisan@redhat.com>
Bug-Url: https://bugzilla.redhat.com/1063996
Reviewed-on: http://gerrit.ovirt.org/25778
Reviewed-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-by: Allon Mureinik <amureini@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>