Make 1.4 compat code call the 1.6 one, reducing
code duplication. Add comment explaining why we can't
make 1.4 call 1.5 as usual.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>