Change KDC constrained-delegation precedence order

MS-SFU errata from 2019/12/09 indicates that legacy constrained
delegation should be prefered over resource-based constrained
delegation, which results slight diferences.

Also clarify that in the get_authdata_info KDB method, the PAC must be
verified and checked for user sensitivity for S4U2Proxy.  Document
that the client name should only be provided in the cross-realm
S4U2Proxy case.

[ghudson@mit.edu: clarified comments and commit message]

https://github.com/krb5/krb5/commit/cf6b710518bd6da8c491ee4020a9ad8ded321d66
Author: Isaac Boukris <iboukris@gmail.com>
Committer: Greg Hudson <ghudson@mit.edu>
Commit: cf6b710518bd6da8c491ee4020a9ad8ded321d66
Branch: master
 src/include/kdb.h         |    9 ++-
 src/kdc/kdc_util.c        |  167 ++++++++++++++++++++------------------------
 src/tests/gssapi/t_s4u.py |   32 ++++++---
 src/tests/t_audit.py      |    2 +-
 4 files changed, 107 insertions(+), 103 deletions(-)