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

tests/testcases/roles/cluster-dump/tasks/main.yml

@@ -2,17 +2,17 @@
 - name: Generate dump folder
   command: "{{ bin_dir }}/kubectl cluster-info dump --all-namespaces --output-directory /tmp/cluster-dump"
   no_log: true
-  when: inventory_hostname in groups['kube-master']
+  when: inventory_hostname in groups['kube_control_plane']
 
 - name: Compress directory cluster-dump
   archive:
     path: /tmp/cluster-dump
     dest: /tmp/cluster-dump.tgz
-  when: inventory_hostname in groups['kube-master']
+  when: inventory_hostname in groups['kube_control_plane']
 
 - name: Fetch dump file
   fetch:
     src: /tmp/cluster-dump.tgz
     dest: "{{ lookup('env', 'CI_PROJECT_DIR') }}/cluster-dump/{{ inventory_hostname }}.tgz"
     flat: true
-  when: inventory_hostname in groups['kube-master']
+  when: inventory_hostname in groups['kube_control_plane']