Add a validator that checks whether provided Directory Manager is valid by attempting to connect to LDAP. Related https://pagure.io/freeipa/issue/6892 Signed-off-by: Tomas Krizek <tkrizek@redhat.com> Reviewed-By: Martin Basti <mbasti@redhat.com> Reviewed-By: Christian Heimes <cheimes@redhat.com> Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>