HPCC-11882 Roxie should use supplied jobname if present

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #6211 from richardkchapman/roxie-jobname

HPCC-11882 Roxie should use supplied jobname if present

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>