title: ‘Jenkins’ missing node label ‘master’ after v. 2.307+ upgrade
body: <p>After upgrading to 2.307 and applying terminology changes (from 'master' to 'Built-In Node'), my builds stopped working with the following error message:
  ‘Jenkins’ doesn’t have label ‘master’</p>
  <p>My Jenkinsfile looks like this:</p>
  <pre><code>
  node('master') {
      dir('build') {
          stage('Checkout') {
              ...
          }
      }
  }
  </code></pre>