Windows: RDR_GetVolumeInfo do not always return success

If the call failed because all servers are down or all instances
of the volume are offline or busy, tell the caller.  Do not return
fake data.

Change-Id: I4e89cefba19161c7d75cfdfd04a1cf7dfc2398f4
Reviewed-on: http://gerrit.openafs.org/9882
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>