Rework traffic checks and timing of traffic report

Because of how piaware started its traffic checks and traffic report, the
report would zero the last-five-minute message counter right before the
traffic check ran, causing them to interact in a way that with low volume
would at least cause excess logging and possibly cause piaware to give up on
the connection and restart it even though there wasn't a problem.

We now schedule the traffic report from within the periodic check, eliminating
the interaction.