Fix error code on clpreauth module failure

Fix error code on clpreauth module failure

Commit 632260bd1fccfb420f0827b59c85c329203eafc9 (ticket #7517) allows
better error reporting for some client pre-authentication failures.
However, it breaks an assumption in the S4U2Self code that such errors
can be recognized by the KRB5_PREAUTH_FAILED error code.  Instead of
passing through the error code reported by the first real preauth
module, wrap that error and return KRB5_PREAUTH_FAILED.

ticket: 8457 (new)
target_version: 1.14-next
target_version: 1.13-next