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/ovn4nfv/tasks/main.yml

@@ -1,9 +1,9 @@
 ---
 - name: ovn4nfv | Label control-plane node
   command: >-
-    {{ bin_dir }}/kubectl label --overwrite node {{ groups['kube-master'] | first }} ovn4nfv-k8s-plugin=ovn-control-plane
+    {{ bin_dir }}/kubectl label --overwrite node {{ groups['kube_control_plane'] | first }} ovn4nfv-k8s-plugin=ovn-control-plane
   when:
-    - inventory_hostname == groups['kube-master'][0]
+    - inventory_hostname == groups['kube_control_plane'][0]
 
 - name: ovn4nfv | Create ovn4nfv-k8s manifests
   template: