Lib: Use plain WSGIServer instead of ThreadingWSGIServer for metrics
Lib: Use plain WSGIServer instead of ThreadingWSGIServer for metrics

ThreadingWSGIServer is not available in the library version in Debian
Buster.
It shouldn't really matter if we used a threading server or not,
Prometheus itself also used to use a WSGIServer.

fausecteam/ctf-gameserver,fausecteam/ctf-gameserver,fausecteam/ctf-gameserver,fausecteam/ctf-gameserver,fausecteam/ctf-gameserver