helm: Allow to specify k8s api-server host and port via env vars

Currently, there are three ways how k8s api-server address can be
passed to cilium-agent:

1. Default: k8s passes it to cilium-agent Pod via KUBERNETES_SERVICE_{HOST,PORT}
   env vars. Usually, it's a ClusterIP which is translated to the master
   node IP address via iptables rules installed by kube-proxy.
2. Via the `--k8s-kubeconfig-path` cilium-agent param. This way seems to be
   unnecessary too complicated because the kubeconfig has to be distributed
   among all cilium nodes, and cilium-agent needs only IP addr + port of
   the api service, as the service account credentials are already
   mounted into cilium-agent Pod [1].
3. Via the `--k8s-api-server` cilium-agent param. Unfortunately, this way
   provides http-only access to the api-server, as pkg/k8s/config.go
   does not try to set certificate authority and token when
   `--k8s-api-server` is set.

This commit introduces a fourth way to pass the address to the api-server
by overriding KUBERNETES_SERVICE_{HOST,PORT} env vars with helm. This is
a temporary workaround needed for the kube-proxy free getting started
guide until the third way has been fixed.

[1]: https://kubernetes.io/docs/tasks/access-application-cluster/access-cluster/#accessing-the-api-from-a-pod

Signed-off-by: Martynas Pumputis <m@lambda.lt>

install/kubernetes/cilium/charts/agent/templates/daemonset.yaml

@@ -69,6 +69,14 @@ spec:
               key: custom-cni-conf
               name: cilium-config
               optional: true
+{{- if .Values.global.k8sServiceHost }}
+        - name: KUBERNETES_SERVICE_HOST
+          value: {{ .Values.global.k8sServiceHost | quote }}
+{{- end }}
+{{- if .Values.global.k8sServicePort }}
+        - name: KUBERNETES_SERVICE_PORT
+          value: {{ .Values.global.k8sServicePort | quote }}
+{{- end }}
 {{- if contains "/" .Values.image }}
         image: "{{ .Values.image }}"
 {{- else }}

install/kubernetes/cilium/charts/operator/templates/deployment.yaml

@@ -110,6 +110,14 @@ spec:
               key: AWS_DEFAULT_REGION
               name: cilium-aws
               optional: true
+{{- if .Values.global.k8sServiceHost }}
+        - name: KUBERNETES_SERVICE_HOST
+          value: {{ .Values.global.k8sServiceHost | quote }}
+{{- end }}
+{{- if .Values.global.k8sServicePort }}
+        - name: KUBERNETES_SERVICE_PORT
+          value: {{ .Values.global.k8sServicePort | quote }}
+{{- end }}
 {{- if contains "/" .Values.image }}
         image: "{{ .Values.image }}"
 {{- else }}