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/metallb/tasks/main.yml

@@ -22,7 +22,7 @@
   register: apparmor_status
   when:
     - podsecuritypolicy_enabled
-    - inventory_hostname == groups['kube-master'][0]
+    - inventory_hostname == groups['kube_control_plane'][0]
   failed_when: false
 
 - name: Kubernetes Apps | Set apparmor_enabled
@@ -30,7 +30,7 @@
     apparmor_enabled: "{{ apparmor_status.rc == 0 }}"
   when:
     - podsecuritypolicy_enabled
-    - inventory_hostname == groups['kube-master'][0]
+    - inventory_hostname == groups['kube_control_plane'][0]
 
 - name: "Kubernetes Apps | Lay Down MetalLB"
   become: true
@@ -38,7 +38,7 @@
   with_items: ["metallb.yml", "metallb-config.yml"]
   register: "rendering"
   when:
-    - "inventory_hostname == groups['kube-master'][0]"
+    - "inventory_hostname == groups['kube_control_plane'][0]"
 
 - name: "Kubernetes Apps | Install and configure MetalLB"
   kube:
@@ -49,7 +49,7 @@
   become: true
   with_items: "{{ rendering.results }}"
   when:
-    - "inventory_hostname == groups['kube-master'][0]"
+    - "inventory_hostname == groups['kube_control_plane'][0]"
 
 - name: Kubernetes Apps | Check existing secret of MetalLB
   command: "{{ bin_dir }}/kubectl --kubeconfig /etc/kubernetes/admin.conf -n metallb-system get secret memberlist"
@@ -57,18 +57,18 @@
   become: true
   ignore_errors: yes
   when:
-    - inventory_hostname == groups['kube-master'][0]
+    - inventory_hostname == groups['kube_control_plane'][0]
 
 - name: Kubernetes Apps | Create random bytes for MetalLB
   command: "openssl rand -base64 32"
   register: metallb_rand
   when:
-    - inventory_hostname == groups['kube-master'][0]
+    - inventory_hostname == groups['kube_control_plane'][0]
     - metallb_secret.rc != 0
 
 - name: Kubernetes Apps | Install secret of MetalLB if not existing
   command: "{{ bin_dir }}/kubectl --kubeconfig /etc/kubernetes/admin.conf -n metallb-system create secret generic memberlist --from-literal=secretkey={{ metallb_rand.stdout }}"
   become: true
   when:
-    - inventory_hostname == groups['kube-master'][0]
+    - inventory_hostname == groups['kube_control_plane'][0]
     - metallb_secret.rc != 0