HPCC-10818 Fix problem with MANY LOOKUP in a child loopp/query

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #5370 from ghalliday/issue10818

HPCC-10818 Fix problem with MANY LOOKUP in a child loopp/query

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>