HPCC-10743 Fix overload mode where channelsPerNode > 2

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #5318 from ghalliday/issue10743

HPCC-10743 Fix overload mode where channelsPerNode > 2

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>