Windows: Use the allocation size from the service

The prior patchset modified the service AllocationSize return value
to count the number of 1KB units.  Use the value from the service
without modification.  This corrects an inconsistency in the
FileStandardInformation response.

Change-Id: I9a5f0a4f43aa12de903875b6ed4c5493e37b0163
Reviewed-on: http://gerrit.openafs.org/11491
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>