Labeling existing namespace that already has the label fails

Job #1354797665 failed for 6c5beb1b:

** Ensuring the review-ar-update-xv0iqr namespace exists... **
Name:         review-ar-update-xv0iqr
Labels:       name=review-ar-update-xv0iqr
              tls=review-apps-tls
Annotations:  <none>
Status:       Terminating
No resource quota.
No LimitRange resource.
** Labeling the review-ar-update-xv0iqr namespace with tls=review-apps-tls **
error: 'tls' already has a value (review-apps-tls), and --overwrite is false

The fix is probably to pass the --overwrite option.