Update Prometheus Kubernetes node discovery

Use new upstream[0] recommended rewrite for discovering Kubernetes nodes
through the API server proxy.

[0]: https://github.com/prometheus/prometheus/pull/2641

files/gitlab-cookbooks/gitlab/libraries/prometheus.rb

@@ -225,16 +225,14 @@ module Prometheus
               'regex' => '__meta_kubernetes_node_label_(.+)',
             },
             {
-              'source_labels' => ['__address__'],
               'target_label' => '__address__',
-              'regex' => '([^:;]+):([0-9]+)',
-              'replacement' => '${1}:10255',
+              'replacement' => 'kubernetes.default.svc:443',
             },
             {
-              'source_labels' => ['__scheme__'],
-              'target_label' => '__scheme__',
-              'regex' => 'https',
-              'replacement' => 'http',
+              'source_labels' => ['__meta_kubernetes_node_name'],
+              'regex' => '(.+)',
+              'target_label' => '__metrics_path__',
+              'replacement' => '/api/v1/nodes/${1}/proxy/metrics',
             },
           ],
           'metric_relabel_configs' => [

spec/chef/recipes/prometheus_spec.rb

@@ -52,16 +52,13 @@ prometheus_yml_output = <<-PROMYML
     relabel_configs:
     - action: labelmap
       regex: __meta_kubernetes_node_label_(.+)
+    - target_label: __address__
+      replacement: kubernetes.default.svc:443
     - source_labels:
-      - __address__
-      target_label: __address__
-      regex: "([^:;]+):([0-9]+)"
-      replacement: "${1}:10255"
-    - source_labels:
-      - __scheme__
-      target_label: __scheme__
-      regex: https
-      replacement: http
+      - __meta_kubernetes_node_name
+      regex: "(.+)"
+      target_label: __metrics_path__
+      replacement: "/api/v1/nodes/${1}/proxy/metrics"
     metric_relabel_configs:
     - source_labels:
       - pod_name