Try kadmin/admin first in libkadm5clnt

The MIT krb5 kadmin protocol originally used kadmin/admin as the
service principal.  Commits 493f0da5fbf92b0ac2f10e887706d1964d8a15e8
and 5cfaec38a8e8f1c4b76228ba0a252987af797ca4 changed it to use
kadmin/hostname preferentially, with kadmin/admin as a fallback, for
interoperability with the Solaris SEAM administrative protocol.

Change the preference order so that kadmin/admin is tried first, with
kadmin/hostname as a fallback.

https://github.com/krb5/krb5/commit/1d282badfbd6098e3db9d50d22d565c2ec3c8c47
Author: Greg Hudson <ghudson@mit.edu>
Commit: 1d282badfbd6098e3db9d50d22d565c2ec3c8c47
Branch: master
 doc/admin/admin_commands/kadmin_local.rst |   14 +++++++-------
 doc/admin/database.rst                    |   10 +++++-----
 src/lib/kadm5/clnt/client_init.c          |   26 ++++++++++----------------
 src/tests/t_kadmin_acl.py                 |   14 ++++++++++++++
 4 files changed, 36 insertions(+), 28 deletions(-)