Windows: refactor volume location updates

Windows: refactor volume location updates

Break out the VL_GetEntryByName RPC calls into support
functions so we can reduce the amount of duplicated code.

Reviewed-on: http://gerrit.openafs.org/5329
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit 9563dd68fc1fb4b86016106aaacd33732d4cf6ed)

Change-Id: I7fc8b9ac2902c0909b39c446468307fba30b2a51
Reviewed-on: http://gerrit.openafs.org/6020
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>