Revise cluster management task

After removing the sections of the page that are not in line with the
content guide, there is little left.

Edit pages that link to removed task to no longer link there.
Redirect using 302 status so that there is a future opportunity to reinstate
the page or something like it.

- Avoid links to removed cluster management task
- Broaden applicability of “Safely Drain A Node”
- Add (stub) cluster upgrade task page
- Add a basic page about upgrading your cluster.
- Add a task page about enabling or disabling HTTP APIs

content/en/docs/concepts/architecture/controller.md

@@ -92,9 +92,8 @@ Controllers that interact with external state find their desired state from
 the API server, then communicate directly with an external system to bring
 the current state closer in line.
 
-(There actually is a controller that horizontally scales the
-nodes in your cluster. See
-[Cluster autoscaling](/docs/tasks/administer-cluster/cluster-management/#cluster-autoscaling)).
+(There actually is a [controller](https://github.com/kubernetes/autoscaler/)
+that horizontally scales the nodes in your cluster.)
 
 The important point here is that the controller makes some change to bring about
 your desired state, and then reports current state back to your cluster's API server.