refactor(fleetctl): Remove unused vars
feat(fleetctl): block forever on load/unload/start/stop
refactor(agent): Move logic from HandleEventJobOffered to MaybeBid
refactor(agent): Move logic from HandleEventJobScheduled to JobScheduled
refactor(agent): Move StopJob locking into Agent
refactor(agent): Move logic from HandleEventJobUnscheduled to JobUnscheduled
refactor(agent): unexport Agent.UnloadJob
refactor(agent): Drop Agent.Machine()
refactor(agent): unexport Agent.LoadJob
refactor(agent): unexport Agent.Bid
refactor(agent): Split JobScheduled into JobScheduledElsewhere/Locally