IPA DC: add missing checks

IPA DC: add missing checks

When introducing FreeIPA support, two places were forgotten:

 - schannel gensec module needs to be aware of IPA DC
 - _lsa_QueryInfoPolicy should treat IPA DC as PDC

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14903

Signed-off-by: Alexander Bokovoy <ab@samba.org>
Reviewed-by: Guenther Deschner <gd@samba.org>
Autobuild-User(master): Alexander Bokovoy <ab@samba.org>
Autobuild-Date(master): Sat Nov 13 07:01:26 UTC 2021 on sn-devel-184

(cherry picked from commit c69b66f649c1d47a7367f7efe25b8df32369a3a5)

Autobuild-User(v4-13-test): Jule Anger <janger@samba.org>
Autobuild-Date(v4-13-test): Mon Nov 15 15:33:17 UTC 2021 on sn-devel-184