HPCC-11553 Fix deadlock if funnel innput hits exception in start

If the parallel version of funnel hits an exception in one of
it's input's start methods, after all others have finished, then
it deadlocked. As long as one of the other inputs was still
going the exception was triggered.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #5973 from jakesmith/hpcc-11553

HPCC-11553 Fix deadlock if funnel input hits exception in start

Reviewed-By: Gavin Halliday <gavin.halliday@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>