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"