remove unimplemented custom_flags vars, document the extra_args vars (issue 4352) (#5108)

docs/vars.md

@@ -160,12 +160,15 @@ kubelet_custom_flags:
   - "--eviction-soft=memory.available<300Mi"
 ```
 The possible vars are:
-* *apiserver_custom_flags*
-* *controller_mgr_custom_flags*
-* *scheduler_custom_flags*
 * *kubelet_custom_flags*
 * *kubelet_node_custom_flags*
 
+Extra flags for the API server, controller, and scheduler components can be specified using these variables, 
+in the form of dicts of key-value pairs of configuration parameters that will be inserted into the kubeadm YAML config file:
+* *kube_kubeadm_apiserver_extra_args*
+* *kube_kubeadm_controller_extra_args*
+* *kube_kubeadm_scheduler_extra_args*
+
 #### User accounts
 
 By default, a user with admin rights is created, named `kube`.

roles/kubernetes/master/defaults/main/main.yml

@@ -136,16 +136,9 @@ kube_webhook_token_auth: false
 ## Variables for webhook token auth https://kubernetes.io/docs/reference/access-authn-authz/authentication/#webhook-token-authentication
 # kube_webhook_token_auth_url: https://...
 
-## Variables for custom flags
-apiserver_custom_flags: []
-
 # List of the preferred NodeAddressTypes to use for kubelet connections.
 kubelet_preferred_address_types: 'InternalDNS,InternalIP,Hostname,ExternalDNS,ExternalIP'
 
-controller_mgr_custom_flags: []
-
-scheduler_custom_flags: []
-
 ## Extra args for k8s components passing by kubeadm
 kube_kubeadm_apiserver_extra_args: {}
 kube_kubeadm_controller_extra_args: {}