If the user opts-out after boot images have been updated, we should support revert to the original boot image that the cluster was originally installed on.  MCO-820 is a pre-req for this as that implements the opt-in mechanism. Implementation details will be hashed out in the enhancement.

Done when:

• revert mechanism is implemented
• tests for revert mechanism are implemented

After some back and forth on the enhancement, we are changing direction to a manual approach. The MCO will maintain a boot image history for a machine management resource, and a method to restore will be provided via docs(MCO-843)

Done when:

• boot image history is stored via a new CR for every machine management resource that is update. This history should contain the time of update, identifying information for the updated image at the very least
• users are able to easily access this CR from the oc client.