Windows: reorg open handle counts and Fcb->NPFcb->Resource

Windows: reorg open handle counts and Fcb->NPFcb->Resource

Reorganize when open handle counts are decremented in order
to avoid a race with worker threads performing garbage collection.

Change-Id: I07c1c5e80fad48cd3439dbc9c85bd6dff9b9bf44
Reviewed-on: http://gerrit.openafs.org/6504
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Peter Scott <pscott@kerneldrivers.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>