Windows: AFSPopulateNameArrayFromRelatedArray change

Modify AFSPopulateNameArrayFromRelatedArray so that the DirectoryCB
parameter can safely be NULL.   A NULL DirectoryCB input is required
to copy the entire NameArray.

Reviewed-on: http://gerrit.openafs.org/9340
Reviewed-by: Rod Widdowson <rdw@steadingsoftware.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit a3a79c5a15bff7e978ff4bae2d2a480b73750392)

Change-Id: I43b1779db30aa345a89d9acd17644d1341a051ed
Reviewed-on: http://gerrit.openafs.org/9384
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>