Windows: Use mtafsutil library when linking with pthreads

Use the multi-threaded version of the util library in a few places
that are linking with pthreads but use the standard version.

Change-Id: I41f780eb5fda841f22fae2d2afb36cc5225e94f1
Reviewed-on: http://gerrit.openafs.org/9844
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-on: http://gerrit.openafs.org/9845