Make defaults for StatsD module more sensible

* Management interface available on localhost interface only.
* Load Graphite and Ganglia backends by default. (The backend modules do
  nothing unless they are configured, so merely loading them does not
  alter behavior.)

Change-Id: Ia24f0a7c0a6af32efed73cbdfea63a7fb8be8af8
Merge "Make defaults for StatsD module more sensible" into production