HPCC-12406 Ensure PIPE files are unique if multiple slaves

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #6533 from jakesmith/hpcc-12406

HPCC-12406 Ensure PIPE files are unique if multiple slaves

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>
HPCC-12390 Allow variable parameters to SAMPLE

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>