Don't accumulate too much work - late hellos

[dtaht]

When slammed with new data or retraction babel has a tendency to send late hellos, and slow boxes drop off the net. I had a logging function for this at one point. And I'd also added compute and other bounds
to the main loop to see where it was going wrong. then I thought threading the whole thing would be better, or using a better timer loop to make sure the hellos got out. Then I lost 2 years.

first up, at least log those.