cleanup http/io debugging
support iterating by target in addition to target_ip
support write_http via collectd
If we pass in NULL, we can assume that someone has been playing
directly on the stats object the whole time, so it is already the
newest state... carry on and do our stuff without overwriting it.
If the current metrics in the stats are empty and the previous stats
are not, show the previous metrics (noting that they are old).
Support asynch_metrics in a nicer way -- at the end of each payload.
Fix the check status.