addons: Update Prometheus to v2.1.0

* Change service discovery to relabel jobs to align with
rule expressions in upstream examples
* Use a separate service account for prometheus instead
of granting roles to the namespace's default
* Use a separate service account for node-exporter
* Update node-exporter and kube-state-metrics exporters

addons/prometheus/exporters/kube-state-metrics/cluster-role.yaml

@@ -35,4 +35,3 @@ rules:
   resources:
   - horizontalpodautoscalers
   verbs: ["list", "watch"]
-