title: Jenkins not deleting old branches from multibranch pipeline
body: <p>When scanning my multibranch pipeline, I am expecting old branches that are deleted from bitbucket to get deleted in Jenkins.
  This is the output of scanning my pipeline:</p>
  <pre><code>Evaluating orphaned items in *****
  Will remove ****
  Will remove ****
  Finished: NOT_BUILT
  </code></pre>
  <p>But it doesn't remove the branches.</p>
  <p>I have Prune setup and orphaned setting are all set to empty</p>
  <p>Edit:
  Tried to add <code>extensions: [[$class: 'PruneStaleBranch']]</code> to my checkout step, it still doesn't remove old branches</p>