Add HA/LB endpoints for kube-apiserver

* Add HA docs for API server.
* Add auto-evaluated internal endpoints and clarify the loadbalancer_apiserver
vars and usecases.
* Use facts for kube_apiserver to not repeat code and enable LB endpoints use.
* Use /healthz check for the wait-for apiserver.
* Use the single endpoint for kubelet instead of the list of apiservers
* Specify kube_apiserver_count to for HA layout

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

roles/kubernetes/master/tasks/main.yml

@@ -26,9 +26,12 @@
   when: apiserver_manifest.changed
 
 - name: wait for the apiserver to be running
-  wait_for:
-    port: "{{kube_apiserver_insecure_port}}"
-    timeout: 60
+  uri: url=http://localhost:8080/healthz
+  register: result
+  until: result.status == 200
+  retries: 10
+  delay: 6
+
 
 # Create kube-system namespace
 - name: copy 'kube-system' namespace manifest