HPCC-11478 IgnoreMissingFiles option not working in Roxie

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #5919 from richardkchapman/ignoreMissingFiles

HPCC-11478 IgnoreMissingFiles option not working in Roxie

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>