Generalize the ephemeral build managers so that any manager may manage a builder spawned by any other manager.

buildman/templates/cloudconfig.yaml

@@ -6,7 +6,7 @@ write_files:
   content: |
     REALM={{ realm }}
     TOKEN={{ token }}
-    ENDPOINT=wss://buildman.quay.io:8787
+    SERVER=wss://{{ manager_hostname }}
 
 coreos:
   update:
@@ -31,7 +31,6 @@ coreos:
         [Service]
         TimeoutStartSec=600
         TimeoutStopSec=2000
-        ExecStartPre=/bin/sh -xc "echo '{{ manager_ip }} buildman.quay.io' >> /etc/hosts; exit 0"
         ExecStartPre=/usr/bin/docker login -u {{ quay_username }} -p {{ quay_password }} -e unused quay.io
         ExecStart=/usr/bin/docker run --rm --net=host --name quay-builder --privileged --env-file /root/overrides.list -v /var/run/docker.sock:/var/run/docker.sock quay.io/coreos/registry-build-worker:latest
         ExecStop=/usr/bin/docker stop quay-builder