HPCC-10776 Spurious "Cannot write file" errors from Roxie

Previous fix was not quite correct.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #5340 from richardkchapman/roxie-write-again

HPCC-10776 Spurious "Cannot write file" errors from Roxie

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>