windows: preserve lasterror prior to calling free

windows: preserve lasterror prior to calling free

free() destroys GetLastError, so preserve it before giving back all the
buffers.  Then if the create process failed we have something sensible to
log.

Reviewed-on: http://gerrit.openafs.org/3175
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit e1ed8ab1d93906e1b556de332fa32601a9a489fc)
Change-Id: I028a96a669fff3db48c05f2d894e9c6ef31fad12
Reviewed-on: http://gerrit.openafs.org/3240
Tested-by: BuildBot <buildbot@rampaginggeek.com>