If you have a site thats not being used alot, you can have as little
as one active process which when it reaches its PassengerPoolIdle,
gets killed. Passenger then will not respawn another instance until a
new request comes in which makes that first request quite a bit
If a thread is being killed due to inactivity and the queue has 0
other threads in it, then it should immediately respawn so that the
next request doesn't have to wait for the application to respawn.