Accelerate packaging: delay queuing when another release with the same project is queued

The packaging pipeline currently runs strictly in serial. We could run them in parallel, but it would be safer to never simultaneously have two workers packaging releases from the same project.

Queuing first goes to beanstalk, then Drupal puts that on the queue in Jenkins. We have state tracking for where each Jenkins job is. If there is already another release from the same project in Jenkins, either queued or executing, we can put it back on the beanstalk queue with a delay.