Installing a primary control plane node on a healthy cluster

The title, use case, and prerequisites for this procedure are confusing. The procedure is based on 411-healthy.md, which describes adding a 4th control plane node to a cluster with 3 healthy CP nodes and then removing one of the original CP nodes.

Task scope:

• New title: "Replacing a control plane node in a healthy cluster". Remove "primary" because it does not make sense.
• Use case: "You can replace a control plane node in a healthy cluster with 3 control plane nodes by adding a new control plane node and removing an existing control plane node."
• Prerequisites:
  • You have installed OpenShift Container Platform 4.11 or later, with the required etcd-operator version.
  • You have added a host to the cluster by using the UI or the API.
  • You have added the annotation role:master to the host to create a new control plane node.
• Step 3: "Confirm the primary node is in Ready status:" -> "Check the node status to verify that the all CP nodes are available:". ('oc get' returns all the nodes. "available" is general enough to cover the different possibilities.)
  • Example output shows 4 CP nodes. That means you see the original 3 CP nodes and the new CP node. It would be helpful to highlight the new CP node using whatever name is used in the  link-machine-and-node.sh script. source
• Step 6: "Confirm the etcd-operator configuration applies to all nodes:" -> "Monitor the etcd-operator configuration process:". The configuration can take a long time. That's why the user needs this command.
• Step 7. 'oc rsh' commands. Will be fixed with HCIDOCS-518.
• Step 8: "Confirm node health:" -> "Verify that all nodes are available:"