HPCC-10113 - Lookup join incorrectly handling KEEP(1)

KEEP(1) in conjunction with MANY and ATMOST could cause
spurious records.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #4896 from jakesmith/hpcc-10113

HPCC-10113 - Lookup join incorrectly handling KEEP(1)

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>