Fix etcd install with docker and etcd_kubeadm_enabled (#5777)

- This solves issue #5721 & #5713 (dupes)
  - Provide a cleaner default usage pattern for the download role
    around etcd that supports 'host' and 'docker' properly
  - Extract the 'etcdctl' as a separate task install piece and reuse it where
    appropriate
  - Update the kubeadm-etcd task to reflect the above change

roles/kubernetes/master/tasks/kubeadm-etcd.yml

@@ -16,3 +16,12 @@
   include_tasks: "{{ role_path }}/../../etcd/tasks/install_host.yml"
   vars:
     etcd_cluster_setup: true
+  when: etcd_deployment_type == "host"
+
+- name: Ensure etcdctl binary is installed
+  include_tasks: "{{ role_path }}/../../etcd/tasks/install_etcdctl_docker.yml"
+  vars:
+    etcd_cluster_setup: true
+    etcd_retries: 4
+  when:
+    - etcd_deployment_type == "docker"

roles/kubernetes/preinstall/tasks/0020-verify-settings.yml

@@ -260,6 +260,12 @@
     msg: "kubeadm etcd mode requires experimental control plane"
   when: etcd_kubeadm_enabled
 
+- name: Stop if etcd deployment type is not host or docker
+  assert:
+    that: etcd_deployment_type in ['host', 'docker']
+    msg: "The etcd deployment type, 'etcd_deployment_type', must be host or docker"
+  run_once: true
+
 - name: Stop if download_localhost is enabled but download_run_once is not
   assert:
     that: download_run_once

roles/kubernetes/preinstall/tasks/0040-set_facts.yml

@@ -185,7 +185,6 @@
     kube_etcd_cacert_file: "etcd/ca.crt"
     kube_etcd_cert_file: "apiserver-etcd-client.crt"
     kube_etcd_key_file: "apiserver-etcd-client.key"
-    etcd_deployment_type: host
   when:
     - etcd_kubeadm_enabled