metrics: don't Panic on bad shutdown

Just log the error.

pkg/services/metrics/metrics.go

@@ -37,6 +37,6 @@ func (ms *Service) ShutDown() {
 	ms.log.Info("shutting down service", zap.String("endpoint", ms.Addr))
 	err := ms.Shutdown(context.Background())
 	if err != nil {
-		ms.log.Panic("can't shut down service")
+		ms.log.Error("can't shut service down", zap.Error(err))
 	}
 }