DRTVWR-476: Pump coroutines a few more times when we start quitting.

By the time "LLApp" listeners are notified that the app is quitting, the
mainloop is no longer running. Even though those listeners do things like
close work queues and inject exceptions into pending promises, any coroutines
waiting on those resources must regain control before they can notice and shut
down properly. Add a final "LLApp" listener that resumes ready coroutines a
few more times.

Make sure every other "LLApp" listener is positioned before that new one.