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/upgrade/pre-upgrade/tasks/main.yml

@@ -21,7 +21,7 @@
     {{ bin_dir }}/kubectl get node {{ kube_override_hostname|default(inventory_hostname) }}
     -o jsonpath='{ range .status.conditions[?(@.type == "Ready")].status }{ @ }{ end }'
   register: kubectl_node_ready
-  delegate_to: "{{ groups['kube-master'][0] }}"
+  delegate_to: "{{ groups['kube_control_plane'][0] }}"
   failed_when: false
   changed_when: false
 
@@ -32,7 +32,7 @@
     {{ bin_dir }}/kubectl get node {{ kube_override_hostname|default(inventory_hostname) }}
     -o jsonpath='{ .spec.unschedulable }'
   register: kubectl_node_schedulable
-  delegate_to: "{{ groups['kube-master'][0] }}"
+  delegate_to: "{{ groups['kube_control_plane'][0] }}"
   failed_when: false
   changed_when: false
 
@@ -49,12 +49,12 @@
   block:
     - name: Cordon node
       command: "{{ bin_dir }}/kubectl cordon {{ kube_override_hostname|default(inventory_hostname) }}"
-      delegate_to: "{{ groups['kube-master'][0] }}"
+      delegate_to: "{{ groups['kube_control_plane'][0] }}"
 
     - name: Check kubectl version
       command: "{{ bin_dir }}/kubectl version --client --short"
       register: kubectl_version
-      delegate_to: "{{ groups['kube-master'][0] }}"
+      delegate_to: "{{ groups['kube_control_plane'][0] }}"
       run_once: yes
       changed_when: false
       when:
@@ -90,6 +90,6 @@
       fail:
         msg: "Failed to drain node {{ inventory_hostname }}"
       when: upgrade_node_fail_if_drain_fails
-  delegate_to: "{{ groups['kube-master'][0] }}"
+  delegate_to: "{{ groups['kube_control_plane'][0] }}"
   when:
     - needs_cordoning