Windows: torture error reporting

Windows: torture error reporting

When LeaveThread() is called and GetLastError() has already
been called, pass the last error value to LeaveThread().  Otherwise,
the GetLastError() call in LeaveThread() may return an inaccurrate
result.

Reviewed-on: http://gerrit.openafs.org/5312
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit 209d59a61ba9614a8b9d231d828f74a3e9bdaa27)

Change-Id: I8f1b5b6431bad4413e7d81c95835ed852fbba16f
Reviewed-on: http://gerrit.openafs.org/6800
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>