middleware/etcd: Use the correct endpoint

The endpoint for etcd as wrongly set if a proxy was configured.
Clean up some documentation in the process as well.

middleware/etcd/handler.go

@@ -73,6 +73,7 @@ func (e Etcd) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i
 		return e.Err(zone, dns.RcodeNameError, state)
 	}
 	if err != nil {
+		println("returning error", err.Error())
 		return dns.RcodeServerFailure, err
 	}