The value of zero is valid <unique_id/> (see
virNodeDeviceGetSCSIHostCaps()) but our RNG does not think so.
Switching the type to 'unsignedInt' does allow value of zero.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>