See Issue 768030 for context.

Instead of being populated by the contents of devserver_list.yaml, puppet should pull down devservers from serverdb (`atest server list -r devserver -s primary` or similar), making serverdb the source of truth on what devservers are in production.

A side benefit is that at the same time (on puppet sync/run) when serverdb is polled and we fill in the shadow_config template, we can resolve names into IPs, and write parallel lists of names and IPs , giving us a reliable fix for Issue 666022.