Should we really use all zones if the user doesn't explicitly set a number (now that the config default val is changed from 3 to null)? On things like AWS, that's probably more zones than is wanted. But then this is an advanced feature so fine to expect power-users to say which zones.

So overall, yes: I agree with your change.

Could you add a `log.info` message though, saying which zones have been chosen (and why).