HPCC-11567 Fix a few warnings picked up by windows build

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #5981 from ghalliday/issue11567

HPCC-11567 Fix a few warnings picked up by windows build

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>