Memory leak if a controller that has shut down is passed to MTRDevice deviceWithNodeID

[bzbarsky-apple]

It looks to me like if we pass a no-longer-running controller to deviceWithNodeID to create an MTRDevice we will:

1. Have a reference cycle.
2. Never break it, because the controller is already shut down.

Maybe the right thing to do in this case is simply to not add the device to the map (which is the state we would be in if we created the device first, and then shut down the controller)...