Return Prometheus deployment to be a worker workload

* Expose etcd metrics to workers so Prometheus can
run on a worker, rather than a controller
* Drop temporary firewall rules allowing Prometheus
to run on a controller and scrape targes
* Related to https://github.com/poseidon/typhoon/pull/175

addons/prometheus/deployment.yaml

@@ -15,12 +15,6 @@ spec:
         name: prometheus
         phase: prod
     spec:
-      nodeSelector:
-        node-role.kubernetes.io/master: ""
-      tolerations:
-      - key: node-role.kubernetes.io/master
-        operator: Exists
-        effect: NoSchedule
       serviceAccountName: prometheus
       containers:
       - name: prometheus