Feature/fix for supervisor

WIP. I'm still doing final testing, there might be more problems.
The management port can be enabled by by specifying a port, but if you set it to a falsy value it will use 8126? So `config.mgmt_port = false` really means enable and `config.mgmt_port = 0` really means 8126 instead of an ephemeral port.

Was the intention merely to prevent statsd from turning on the management interface?