Warn if balancer is disabled while draining shard

We are constantly getting bit in Atlas by shard draining that is "stuck" because the customer has disabled the balancer. Inevitably, we spend time looking through the logs for a "problem" and finally realize the balancer is off. Draining a shard with the balancer off is not a normal configuration. Could we please log a message about this in the logs, periodically?

One possible solution would be to make the balancer check if some shard needs to be drain even if balancing have been disabled and periodically log a warning.