s3:utils: Allow ROLE_IPA_DC to allow to use Kerberos in gensec

s3:utils: Allow ROLE_IPA_DC to allow to use Kerberos in gensec

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15891

Signed-off-by: Pavel Filipenský <pfilipensky@samba.org>
Reviewed-by: Alexander Bokovoy <ab@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>
Autobuild-User(master): Andreas Schneider <asn@cryptomilk.org>
Autobuild-Date(master): Tue Aug  5 14:51:51 UTC 2025 on atb-devel-224

(cherry picked from commit a4dff82e45308db3ccabac2a55c03d52f04d7b4d)

Autobuild-User(v4-22-test): Jule Anger <janger@samba.org>
Autobuild-Date(v4-22-test): Mon Aug 11 07:53:47 UTC 2025 on atb-devel-224