Replace kube-master with kube_control_plane (#7256)

This replaces kube-master with kube_control_plane because of [1]:

  The Kubernetes project is moving away from wording that is
  considered offensive. A new working group WG Naming was created
  to track this work, and the word "master" was declared as offensive.
  A proposal was formalized for replacing the word "master" with
  "control plane". This means it should be removed from source code,
  documentation, and user-facing configuration from Kubernetes and
  its sub-projects.

NOTE: The reason why this changes it to kube_control_plane not
      kube-control-plane is for valid group names on ansible.

[1]: https://github.com/kubernetes/enhancements/blob/master/keps/sig-cluster-lifecycle/kubeadm/2067-rename-master-label-taint/README.md#motivation

roles/kubernetes-apps/metrics_server/tasks/main.yml

@@ -2,14 +2,14 @@
 # If all masters have node role, there are no tainted master and toleration should not be specified.
 - name: Check all masters are node or not
   set_fact:
-    masters_are_not_tainted: "{{ groups['kube-node'] | intersect(groups['kube-master']) == groups['kube-master'] }}"
+    masters_are_not_tainted: "{{ groups['kube-node'] | intersect(groups['kube_control_plane']) == groups['kube_control_plane'] }}"
 
 - name: Metrics Server | Delete addon dir
   file:
     path: "{{ kube_config_dir }}/addons/metrics_server"
     state: absent
   when:
-    - inventory_hostname == groups['kube-master'][0]
+    - inventory_hostname == groups['kube_control_plane'][0]
   tags:
     - upgrade
 
@@ -21,7 +21,7 @@
     group: root
     mode: 0755
   when:
-    - inventory_hostname == groups['kube-master'][0]
+    - inventory_hostname == groups['kube_control_plane'][0]
 
 - name: Metrics Server | Templates list
   set_fact:
@@ -43,7 +43,7 @@
   with_items: "{{ metrics_server_templates }}"
   register: metrics_server_manifests
   when:
-    - inventory_hostname == groups['kube-master'][0]
+    - inventory_hostname == groups['kube_control_plane'][0]
 
 - name: Metrics Server | Apply manifests
   kube:
@@ -54,4 +54,4 @@
     state: "latest"
   with_items: "{{ metrics_server_manifests.results }}"
   when:
-    - inventory_hostname == groups['kube-master'][0]
+    - inventory_hostname == groups['kube_control_plane'][0]