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/download/defaults/main.yml

@@ -30,7 +30,7 @@ download_container: true
 # if this is set to true, uses the localhost for download_run_once mode
 # (requires docker and sudo to access docker). You may want this option for
 # local caching of docker images or for Flatcar Container Linux by Kinvolk cluster nodes.
-# Otherwise, uses the first node in the kube-master group to store images
+# Otherwise, uses the first node in the kube_control_plane group to store images
 # in the download_run_once mode.
 download_localhost: false
 
@@ -42,8 +42,8 @@ download_always_pull: false
 # SSL validation of get_url module. Note that kubespray will still be performing checksum validation.
 download_validate_certs: true
 
-# Use the first kube-master if download_localhost is not set
-download_delegate: "{% if download_localhost %}localhost{% else %}{{ groups['kube-master'][0] }}{% endif %}"
+# Use the first kube_control_plane if download_localhost is not set
+download_delegate: "{% if download_localhost %}localhost{% else %}{{ groups['kube_control_plane'][0] }}{% endif %}"
 
 # Arch of Docker images and needed packages
 image_arch: "{{host_architecture | default('amd64')}}"
@@ -733,7 +733,7 @@ downloads:
     owner: "root"
     mode: "0755"
     groups:
-    - kube-master
+    - kube_control_plane
 
   crictl:
     file: true
@@ -883,7 +883,7 @@ downloads:
     owner: "root"
     mode: "0755"
     groups:
-    - kube-master
+    - kube_control_plane
 
   weave_kube:
     enabled: "{{ kube_network_plugin == 'weave' }}"
@@ -973,7 +973,7 @@ downloads:
     tag: "{{ coredns_image_tag }}"
     sha256: "{{ coredns_digest_checksum|default(None) }}"
     groups:
-    - kube-master
+    - kube_control_plane
 
   nodelocaldns:
     enabled: "{{ enable_nodelocaldns }}"
@@ -991,7 +991,7 @@ downloads:
     tag: "{{ dnsautoscaler_image_tag }}"
     sha256: "{{ dnsautoscaler_digest_checksum|default(None) }}"
     groups:
-    - kube-master
+    - kube_control_plane
 
   testbox:
     enabled: false
@@ -1011,7 +1011,7 @@ downloads:
     owner: "root"
     mode: "0755"
     groups:
-    - kube-master
+    - kube_control_plane
 
   registry:
     enabled: "{{ registry_enabled }}"
@@ -1038,7 +1038,7 @@ downloads:
     tag: "{{ metrics_server_image_tag }}"
     sha256: "{{ metrics_server_digest_checksum|default(None) }}"
     groups:
-    - kube-master
+    - kube_control_plane
 
   addon_resizer:
     # Currently addon_resizer is only used by metrics server
@@ -1048,7 +1048,7 @@ downloads:
     tag: "{{ addon_resizer_image_tag }}"
     sha256: "{{ addon_resizer_digest_checksum|default(None) }}"
     groups:
-    - kube-master
+    - kube_control_plane
 
   local_volume_provisioner:
     enabled: "{{ local_volume_provisioner_enabled }}"
@@ -1219,7 +1219,7 @@ downloads:
     tag: "{{ dashboard_image_tag }}"
     sha256: "{{ dashboard_digest_checksum|default(None) }}"
     groups:
-    - kube-master
+    - kube_control_plane
 
   dashboard_metrics_scrapper:
     enabled: "{{ dashboard_enabled }}"
@@ -1228,7 +1228,7 @@ downloads:
     tag: "{{ dashboard_metrics_scraper_tag }}"
     sha256: "{{ dashboard_digest_checksum|default(None) }}"
     groups:
-    - kube-master
+    - kube_control_plane
 
 download_defaults:
   container: false