Now a10-watchdog can launch and monitor the status of another program

It turns out that just running watchdog as a standalone separate
process is not 100% reliable. In some rare cases the test program
('scan-for-best-tpr3.rb') may segfault without deadlocking the
hardware. So now a10-watchdog is able to launch and monitor the
health of scan-for-best-tpr3.rb too.