gitlab-ci/autobuild: Add new build confirming behaviour on older MIT Kerberos

gitlab-ci/autobuild: Add new build confirming behaviour on older MIT Kerberos

Because the MIT KDC builds are moving to current MIT and out of the default autobuild
this ensures that on our default host, which is closer to what most of our
users operate, Samba still works with Kerberos.

This uses the ktest environment that does not require the KDC to exist
and instead uses a static ccache and keytab.

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>
BUG: https://bugzilla.samba.org/show_bug.cgi?id=14817
(cherry picked from commit 6145c388d201d817444322dee67ca1ec1989ecd1)