HPCC-9445 Fix leak reporting for packed allocators

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #4534 from ghalliday/issue9445

HPCC-9445 Fix leak reporting for packed allocators

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>