Task scope: Replace RHEL version number with attribute when appropriate.

https://docs.redhat.com/en/documentation/red_hat_satellite/6.16/html-single/overview_concepts_and_deployment_considerations/index

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  RHEL 8 reference needs to be updated:

https://docs.redhat.com/en/documentation/red_hat_satellite/6.16/html-single/overview_concepts_and_deployment_considerations/index#sect-Satellite_Server_Configuration