Purge legacy cleanup tasks from older than 1 year (#4450)

We don't need to support upgrades from 2 year old installs,
just from the last major version.

Also changed most retried tasks to 1s delay instead of longer.

roles/network_plugin/flannel/tasks/main.yml

@@ -1,6 +1,4 @@
 ---
-- import_tasks: pre-upgrade.yml
-
 - name: Flannel | Create Flannel manifests
   template:
     src: "{{item.file}}.j2"

roles/network_plugin/flannel/tasks/pre-upgrade.yml

@@ -1,19 +0,0 @@
----
-- name: Flannel pre-upgrade | Purge legacy flannel systemd unit file
-  file:
-    path: "/etc/systemd/system/docker.service.d/flannel-options.conf"
-    state: absent
-  notify:
-    - Flannel | delete default docker bridge
-
-- name: Flannel pre-upgrade | Purge legacy Flannel static pod manifest
-  file:
-    path: "{{ kube_manifest_dir }}/flannel-pod.manifest"
-    state: absent
-  notify:
-    - Flannel | delete flannel interface
-
-- name: Flannel pre-upgrade | Remove Flannel's certificate directory not required by CNI
-  file:
-    dest: "{{ flannel_cert_dir }}"
-    state: absent