HPCC-9630 - Clear up some exception handling

Various places, were incorrectly handling the ownership of an
IException passed to IExceptionHandler::fireException.
In some cases resulting in a leaked exception, or worse, a -ve leak.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Minor change following review
Merge pull request #4602 from jakesmith/hpcc-9630

HPCC-9630 - Clear up some exception handling

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>