HPCC-9633 - Watchdog crash if collects after shutdown

If the watchdog happens to be about to collect progress/stats
when thor is shutting down, it could crash. Check if stopping
after sleep and quit before collecting

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #4606 from jakesmith/hpcc-9633

HPCC-9633 - Watchdog crash if collects after shutdown

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>