Allow client canonicalization in non-krbtgt AS-REP

Allow client canonicalization in non-krbtgt AS-REP

If a caller makes an AS-REQ with the canonicalize flag set (or with an
enterprise client principal or the anonymous flag), always allow the
KDC to change the client principal.  Continue to restrict server name
changes to requests for TGS principals.

Also remove the conditional for setting canon_ok for fully anonymous
requests.  Both kinds of anonymous requests change the client
principal or realm, but neither kind changes the server principal or
realm, so this logic is no longer needed now that canon_ok only
applies to server name changes.

[ghudson@mit.edu: clarified commit message; removed anonymous PKINIT
clause]

ticket: 8843 (new)