pointer in a local thread. While this is unlikely to significantly
improve performance given modern compiler behavior, it makes the code
more readable and reduces diffs to the Mac OS X version of the same
code (which stores things in creds in the same way, but where the
cred for a thread is reached quite differently).
Discussed with: sson
MFC after: 1 month
Sponsored by: Apple Inc.
Obtained from: TrustedBSD Project
ea0b860502