Windows: AFSProcessOverwriteSupersede CcSetFileSizes

Windows: AFSProcessOverwriteSupersede CcSetFileSizes

Instead of calling CcPurgeCacheSection() in AFSProcessOverwriteSupersede()
as part of the file length truncation to zero, call CcSetFileSizes().

Wait to call CcSetFileSizes() until after the Fcb->Resource has been
dropped but while the Fcb->Header.PagingIoResource is still held.
Make sure that file sizes are restored in the Fcb->Header if the
afsd_service rejects the file update.

Change-Id: I7574e80781ac1dbbe69814c69644bb3825de9b6a
Reviewed-on: http://gerrit.openafs.org/7220
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>