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/network_plugin/kube-router/tasks/annotate.yml

@@ -1,21 +1,21 @@
 ---
-- name: kube-router | Add annotations on kube-master
+- name: kube-router | Add annotations on kube_control_plane
   command: "{{ bin_dir }}/kubectl annotate --overwrite node {{ ansible_hostname }} {{ item }}"
   with_items:
   - "{{ kube_router_annotations_master }}"
-  delegate_to: "{{ groups['kube-master'][0] }}"
-  when: kube_router_annotations_master is defined and inventory_hostname in groups['kube-master']
+  delegate_to: "{{ groups['kube_control_plane'][0] }}"
+  when: kube_router_annotations_master is defined and inventory_hostname in groups['kube_control_plane']
 
 - name: kube-router | Add annotations on kube-node
   command: "{{ bin_dir }}/kubectl annotate --overwrite node {{ ansible_hostname }} {{ item }}"
   with_items:
   - "{{ kube_router_annotations_node }}"
-  delegate_to: "{{ groups['kube-master'][0] }}"
+  delegate_to: "{{ groups['kube_control_plane'][0] }}"
   when: kube_router_annotations_node is defined and inventory_hostname in groups['kube-node']
 
 - name: kube-router | Add common annotations on all servers
   command: "{{ bin_dir }}/kubectl annotate --overwrite node {{ ansible_hostname }} {{ item }}"
   with_items:
   - "{{ kube_router_annotations_all }}"
-  delegate_to: "{{ groups['kube-master'][0] }}"
+  delegate_to: "{{ groups['kube_control_plane'][0] }}"
   when: kube_router_annotations_all is defined and inventory_hostname in groups['k8s-cluster']

roles/network_plugin/kube-router/tasks/main.yml

@@ -55,5 +55,5 @@
   template:
     src: kube-router.yml.j2
     dest: "{{ kube_config_dir }}/kube-router.yml"
-  delegate_to: "{{ groups['kube-master'] | first }}"
+  delegate_to: "{{ groups['kube_control_plane'] | first }}"
   run_once: true