HPCC-11639 Don't include file positions on WU results written to disk

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #6657 from ghalliday/issue11639

HPCC-11639 Don't include file positions on WU results written to disk

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>