Agent's notion of "completed" frameworks is actually "idle" frameworks.

Currently, when a framework goes "idle" on the agent, that is, it no longer has active tasks or executors, the agent transitions it to "completed". Whereas the master considers a framework "completed" when has unregistered or is removed. As a result, the agent has to "uncomplete" frameworks should more tasks arrive for it.

Ideally, the agent stores these frameworks accurately as "idle", and only marks them "completed" when the master tells it to.