Replace Aegir from www-prod-2
We do not really use Aegir on www-prod-2. It was useful at some point for helping to clone dev sites, but now it's more in the way and causing trouble, rather than helping.
I would still like to make sure that a future setup will be aligned with what Symbiotic uses, since I have to support both (and Spark, where Aegir is currently harder to replace). It will likely be based on the Ansible work by Megaphone Jon.