Add testing helper to create labeled namespaces

[#165900520](https://www.pivotaltracker.com/story/show/165900520)

testing/machine/machine.go

@@ -50,10 +50,16 @@ func NewMachine() Machine {
 
 // CreateNamespace creates a namespace, it doesn't return an error if the namespace exists
 func (m *Machine) CreateNamespace(namespace string) (TearDownFunc, error) {
+	return m.CreateLabeledNamespace(namespace, map[string]string{})
+}
+
+// CreateLabeledNamespace creates a namespace, it doesn't return an error if the namespace exists
+func (m *Machine) CreateLabeledNamespace(namespace string, labels map[string]string) (TearDownFunc, error) {
 	client := m.Clientset.CoreV1().Namespaces()
 	ns := &corev1.Namespace{
 		ObjectMeta: metav1.ObjectMeta{
-			Name: namespace,
+			Name:   namespace,
+			Labels: labels,
 		},
 	}
 	_, err := client.Create(ns)