qmp_event_notification: watchdog "debug" and "none" tests reported false ERROR on clean-up

[rayx]

This was because the test checked dmesg output on exit and found a message like this:

[  459.424792] i6300esb: Unexpected close, not stopping watchdog!

The message was not an error. It was just a user-friendly reminder that closing /dev/watchdog didn't stop it (user should do "echo V >/dev/watchdog" instead).

To avoid the message (and hence the false ERROR result), the test needs to keep the file open before it checks dmesg. I think something like the following should do the trick:

# sh -c "echo 0; sleep 360" > /dev/watchdog &