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.
This seems very dangerous. This static variable is read & written from several threads. At the very least add synchronization around it. Better yet, elevate it out of the static realm into a threadsafe object.