Added livenessProbe for local nginx apiserver proxy liveness probe (#4222)

* Added configurable local apiserver proxy liveness probe

* Enable API LB healthcheck by default

* Fix template spacing and moved healthz location to nginx http section

* Fix healthcheck listen address to allow kubelet request healthcheck

roles/kubernetes/node/templates/manifests/nginx-proxy.manifest.j2

@@ -25,6 +25,12 @@ spec:
         memory: {{ nginx_memory_requests }}
     securityContext:
       privileged: true
+    {% if nginx_kube_apiserver_healthcheck_port is defined -%}
+    livenessProbe:
+      httpGet:
+        path: /healthz
+        port: {{ nginx_kube_apiserver_healthcheck_port }}
+    {% endif -%}
     volumeMounts:
     - mountPath: /etc/nginx
       name: etc-nginx