Comment 0 for bug 1719006

1. Add a post job to all branches that publish a constraints/$series.txt to $series
  * On the master branch we publish both master.txt and $series.txt (currently queens.txt)
  * when we fork rocky from master we update the publish job to publish master and rocky.txt.
  * As Doug points out there is a timing race here but it's much smaller than the one we have now.

2. Get projects to use it