Remove rkt support (#4671)

roles/etcd/tasks/install_rkt.yml

@@ -1,30 +0,0 @@
----
-- name: Trust etcd container
-  command: >-
-    /usr/bin/rkt trust
-    --skip-fingerprint-review
-    --root
-    https://quay.io/aci-signing-key
-  register: etcd_rkt_trust_result
-  until: etcd_rkt_trust_result.rc == 0
-  retries: 4
-  delay: "{{ retry_stagger | random + 3 }}"
-  changed_when: false
-  environment: "{{proxy_env}}"
-  when: etcd_cluster_setup
-
-- name: Install | Copy etcdctl binary from rkt container
-  command: >-
-    /usr/bin/rkt run
-    --volume=bin-dir,kind=host,source={{ bin_dir}},readOnly=false
-    --mount=volume=bin-dir,target=/host/bin
-    {{ etcd_image_repo }}:{{ etcd_image_tag }}
-    --name=etcdctl-binarycopy
-    --exec=/bin/cp -- /usr/local/bin/etcdctl /host/bin/etcdctl
-  register: etcd_task_result
-  until: etcd_task_result.rc == 0
-  retries: 4
-  delay: "{{ retry_stagger | random + 3 }}"
-  changed_when: false
-  environment: "{{proxy_env}}"
-  when: etcd_cluster_setup