Document process to update expired credentials

There are some credentials that are setup during the build of the ISO. When these credentials expire, users will need a process to update them with new credentials.

For example, Ironbank credentials are used in the iso builder config nexus script to setup a proxy repo to registry1 and they are also built in to the babu-cache service here.

There may be more credentials we need to consider. Investigate credentials that are configured in the ISO build and document a process to update them on an edge orchestration device that is in use.