Add steps for shutting down an OCP cluster gracefully

[rguske]

Add some helpful hints, loops and scripts for shutting down an OCP cluster gracefully.

Some sources:

• https://hackmd.io/@johnsimcall/HJXwaZkJC?utm_source=preview-mode&utm_medium=rec
• https://docs.redhat.com/en/documentation/openshift_container_platform/4.17/html/backup_and_restore/graceful-shutdown-cluster#prerequisites