HPCC-10933 Excessive "Reset without stop" tracing

Make sure that ifaction/whenaction stop unused upstream activities as soon as
possible.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #5500 from richardkchapman/ifaction-stop

HPCC-10933 Excessive "Reset without stop" tracing

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>