Worker Host Session and Clean Shutdown for StickyTasklist

[longquanzheng]

With stickyTTL, expiring the sticky tasklists is very in-efficient, and the experience is not perfect : after worker host restarted, all the workflows in the cache have to wait for TTL. During the wait, lots of Querys and decisions are still scheduled to sticky tasklists and waiting to timeout.

Ideally, when worker host restarted, it should inform server(history engine) that the stickyTasklist is gone. So that any future activities/querys should not be scheduled to it.

We can keep a small LRU cache for thos "expired" session/stickyTaskList.

[mfateev]

Another option is to have task list itself marked as deleted and immediately refuse addTask requests.