Previously, the du plugin was collecting data every 20 seconds but
carbon was configured to only keep data every 12 hours causing much
confusion.
In the process of reworking this, it was determined:
* No need to collect disk usage info over time. Not sure how that is useful
* Instead, collect CPU/Network/Block info over time. We get this now from docker stats
* We also collect info about the services (addon containers)
* No need to reconfigure collectd for each app change anymore since there is no per
app collectd configuration anymore.
