ipatests: add check_if_sssd_is_online
Split wait_for_sssd_domain_status_online so that we can easily check
that SSSD considers the IPA domain online with check_if_sssd_is_online.
Related: https://pagure.io/freeipa/issue/8510
Signed-off-by: François Cami <fcami@redhat.com>
Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>