Fix potential panic in getMachineConfigOperatorPod when no pods are returned

## Summary In `test/extended-priv/util.go`, the helper function `getMachineConfigOperatorPod` indexes `pods[0]` before checking whether `exutil.GetAllPodsWithLabel` succeeded or returned any pods. This can cause a runtime panic if the label query errors or returns an empty list. ## Related - PR: https://github.com/openshift/machine-config-operator/pull/5875 - Review comment: https://github.com/openshift/machine-config-operator/pull/5875#discussion_r3128857555 - Jira: https://redhat.atlassian.net/browse/MCO-2243 - Requested by: @ptalgulk01 ## Proposed Fix ```go func getMachineConfigOperatorPod(oc *exutil.CLI) (string, error) { pods, err := exutil.GetAllPodsWithLabel(oc.AsAdmin(), MachineConfigNamespace, "k8s-app=machine-config-operator") if err != nil { return "", err } if len(pods) == 0 { return "", fmt.Errorf("no machine-config-operator pod found in namespace %s", MachineConfigNamespace) } logger.Infof("machine-config-operator pod name is %s", pods[0]) return pods[0], nil } ```