HEIMDAL:kdc: Fix transit path validation CVE-2017-6594

HEIMDAL:kdc: Fix transit path validation CVE-2017-6594

Commit f469fc6 (2010-10-02) inadvertently caused the previous hop realm
to not be added to the transit path of issued tickets.  This may, in
some cases, enable bypass of capath policy in Heimdal versions 1.5
through 7.2.

Note, this may break sites that rely on the bug.  With the bug some
incomplete [capaths] worked, that should not have.  These may now break
authentication in some cross-realm configurations.

(similar to heimdal commit b1e699103f08d6a0ca46a122193c9da65f6cf837)

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12998

Reviewed-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Wed Oct 20 10:58:37 UTC 2021 on sn-devel-184