vol: fix namei_ListAFSSubDirs on Windows

vol: fix namei_ListAFSSubDirs on Windows

The directory level represented by 'dirp2' does not exist on
Windows.  Do not attempt to close the DIR object that was
never opened.

Remove unnecessary function prototypes.

Reviewed-on: http://gerrit.openafs.org/3703
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 141aca818ef9e5a6af309edc9512cc5cfee38e90)

Change-Id: I640d834f0bfd6490cf43183843d771f792f7fc06
Reviewed-on: http://gerrit.openafs.org/3850
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>