HPCC-8542 - Ensure skew min/max present

For counts < # slaves, the min/max node and skew were missing

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #3908 from jakesmith/hpcc-8542

HPCC-8542 - Ensure skew min/max present

Reviewed-By: Gavin Halliday <gavin.halliday@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>