Orchestrator should tell inactive workers to power down

[abyrne55]

Currently, when the orchestrator receives a worker request from a worker that's not registered in WORKERS (even if it is registered in AVAILABLE_WORKERS), its default behavior is to just drop the connection:

        try:
            w = WORKERS[str(self.worker_id)]
        except KeyError:
            log.error("Worker with unknown ID %s attempted to connect", self.worker_id)
            return

We'd be much better-served by telling such a worker to power-down by changing the default behavior shown above, and/or by updating the Worker state machine to tell inactive workers to power-off. This would minimize the power draw of inactive workers.

[abyrne55]

Fixed in 609d1a8