s4:kdc: Adapt to removal of publicly accessible request structure members

s4:kdc: Adapt to removal of publicly accessible request structure members

We now have to use the accessor functions instead.

This is an adaptation to Heimdal:

commit ec24edf7005c340018450a202d27ca75fcf322d4
Author: Luke Howard <lukeh@padl.com>
Date:   Thu Jan 20 09:15:24 2022 +1100

    kdc: add accessor functions for KDC request structure

    Add accessor functions for use by Samba and other plugin developers.
    Documentation is in kdc/kdc-accessors.h.

NOTE: THIS COMMIT WON'T COMPILE/WORK ON ITS OWN!

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14995

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
(cherry picked from commit 9399a15fabb5a1b8470b1069a098132e2fdb7f0f)