Log fix: include server princ in kdc log msg under more conditions.
do_as_req.c: After parsing the client, immediately parse the server before
searching for the client princ in KDB.
do_tgs_req.c: After parsing the client principal, set the server principal
to the specified server principal in the request. We later set it normally
based on successfully finding the server in kdb, but this ensures we log
the attempt with more information (which improves diagnostics).