Add labels to namespaces created during end to end tests

Besides that it is a good practice to label resources created this allows in this case easy deletion of the namespaces if:
- there was an issue while running the tests
- the variable TEST_KEEP_NAMESPACES was set
- the tests were abruptly stopped by the developer

Currently you have to run something like:
$ kubectl get namespaces --no-headers=true -o custom-columns=:metadata.name | grep arendelle | xargs kubectl delete namespace
This would become:
$ kubectl delete ns -l "tekton.dev/test-e2e=true"

test/init_test.go

@@ -124,9 +124,13 @@ func initializeLogsAndMetrics(t *testing.T) {
 
 func createNamespace(t *testing.T, namespace string, kubeClient *knativetest.KubeClient) {
  t.Logf("Create namespace %s to deploy to", namespace)
+ labels := map[string]string{
+ "tekton.dev/test-e2e": "true",
+ }
  if _, err := kubeClient.Kube.CoreV1().Namespaces().Create(&corev1.Namespace{
  ObjectMeta: metav1.ObjectMeta{
- Name: namespace,
+ Name: namespace,
+ Labels: labels,
  },
  }); err != nil {
  t.Fatalf("Failed to create namespace %s for tests: %s", namespace, err)

test/v1alpha1/init_test.go

@@ -124,9 +124,13 @@ func initializeLogsAndMetrics(t *testing.T) {
 
 func createNamespace(t *testing.T, namespace string, kubeClient *knativetest.KubeClient) {
  t.Logf("Create namespace %s to deploy to", namespace)
+ labels := map[string]string{
+ "tekton.dev/test-e2e": "true",
+ }
  if _, err := kubeClient.Kube.CoreV1().Namespaces().Create(&corev1.Namespace{
  ObjectMeta: metav1.ObjectMeta{
- Name: namespace,
+ Name: namespace,
+ Labels: labels,
  },
  }); err != nil {
  t.Fatalf("Failed to create namespace %s for tests: %s", namespace, err)