Report Datadog metrics on missing repositories

The pipelines from the following repositories are missing the piece of code to set the pod labels, thus the Datadog tags. Consequently, no metrics are reported for these pipelines. Let's add the missing stage to all pipelines.

• https://github.com/nuxeo/platform-ci-tools
• https://github.com/nuxeo/integration-scripts-priv/

    stage('Set labels') {
      steps {
        container('maven') {
          script {
            nxK8s.setPodLabels()
          }
        }
      }
    }