Windows: AFSClose() DirOpenReferenceCount handling

Unless the caller of AFSRemoveCcb() steals the DirectoryCB object
from the AFSCcb before calling AFSRemoveCcb(), AFSRemoveCcb() will
release the reference count.

In all but one case where the DirectoryCB must be accessed after
the AFSCcb is destroyed AFSClose() can now let AFSRemoveCcb() do the
work.

Change-Id: I8d631d79b2465cd6f2e31444fd052270b078915c
Reviewed-on: http://gerrit.openafs.org/8854
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>