Enable Prometheus provider cleanup when only the router's metrics lev…

…el is activated

Co-authored-by: Kevin Pollet <[email protected]>

cmd/traefik/traefik.go

@@ -298,7 +298,7 @@ func setupServer(staticConfiguration *static.Configuration) (*server.Server, err
 	watcher.AddListener(switchRouter(routerFactory, serverEntryPointsTCP, serverEntryPointsUDP))
 
 	// Metrics
-	if metricsRegistry.IsEpEnabled() || metricsRegistry.IsSvcEnabled() {
+	if metricsRegistry.IsEpEnabled() || metricsRegistry.IsRouterEnabled() || metricsRegistry.IsSvcEnabled() {
 		var eps []string
 		for key := range serverEntryPointsTCP {
 			eps = append(eps, key)