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/ansible/tasks/main.yml

@@ -9,12 +9,12 @@
   until: result.status == 200
   retries: 20
   delay: 1
-  when: inventory_hostname == groups['kube-master'][0]
+  when: inventory_hostname == groups['kube_control_plane'][0]
 
 - name: Kubernetes Apps | Cleanup DNS
   import_tasks: cleanup_dns.yml
   when:
-    - inventory_hostname == groups['kube-master'][0]
+    - inventory_hostname == groups['kube_control_plane'][0]
   tags:
     - upgrade
     - coredns
@@ -24,7 +24,7 @@
   import_tasks: "coredns.yml"
   when:
     - dns_mode in ['coredns', 'coredns_dual']
-    - inventory_hostname == groups['kube-master'][0]
+    - inventory_hostname == groups['kube_control_plane'][0]
   tags:
     - coredns
 
@@ -32,7 +32,7 @@
   import_tasks: "nodelocaldns.yml"
   when:
     - enable_nodelocaldns
-    - inventory_hostname == groups['kube-master'] | first
+    - inventory_hostname == groups['kube_control_plane'] | first
   tags:
     - nodelocaldns
 
@@ -50,7 +50,7 @@
     - "{{ nodelocaldns_manifests.results | default({}) }}"
   when:
     - dns_mode != 'none'
-    - inventory_hostname == groups['kube-master'][0]
+    - inventory_hostname == groups['kube_control_plane'][0]
     - not item is skipped
   register: resource_result
   until: resource_result is succeeded