monitoring: update label on prometheus resources

Updating the promethes reources (PrometheusRule and ServiceMonitor) is
done by fetching the current resource from the server and updating the
spec on it. This commit makes it also apply the labels, so users can
update them via rook CRDs.

Closes: #9241
Signed-off-by: Mara Sophie Grosch <littlefox@lf-net.org>

pkg/operator/k8sutil/prometheus.go

@@ -80,6 +80,7 @@ func CreateOrUpdateServiceMonitor(serviceMonitorDefinition *monitoringv1.Service
 		return nil, fmt.Errorf("failed to retrieve servicemonitor. %v", err)
 	}
 	oldSm.Spec = serviceMonitorDefinition.Spec
+	oldSm.ObjectMeta.Labels = serviceMonitorDefinition.ObjectMeta.Labels
 	sm, err := client.MonitoringV1().ServiceMonitors(namespace).Update(ctx, oldSm, metav1.UpdateOptions{})
 	if err != nil {
 		return nil, fmt.Errorf("failed to update servicemonitor. %v", err)
@@ -123,6 +124,7 @@ func CreateOrUpdatePrometheusRule(prometheusRule *monitoringv1.PrometheusRule) (
 			return nil, fmt.Errorf("failed to get prometheusRule object. %v", err)
 		}
 		promRule.Spec = prometheusRule.Spec
+		promRule.ObjectMeta.Labels = prometheusRule.ObjectMeta.Labels
 		_, err = client.MonitoringV1().PrometheusRules(namespace).Update(ctx, promRule, metav1.UpdateOptions{})
 		if err != nil {
 			return nil, fmt.Errorf("failed to update prometheusRule. %v", err)