Tweaking registrar to only send the metric corresponding to the Worker State

Changing the Registrar to expose the Worker State metric.

The worker state is now being fetched and parsed for use in the dashboard. The related changes can be seen in this PR: https://github.com/ess-dmsc/server-dashboard/pull/35

It has been tested on the filewriter0625.daq.esss.dk and you can see its output by checking http://filewriter0625:9999/ on a SOCKS server enabled browser