previous evaluators checking back in for driver HA

handle the process of evaluators checking back in when driver restart, mark things as we go, currently on to local FS. better things can be done when we have the 2.4.1 fix with which we can have list of previous containers properly.
Ah, thanks! I remember :-) Can we have them share the same threadpool as their siblings? That way events will be produced in a predictable order.