Downstream MCE support with channels

[jnpacker]

Description of the change:

• Add support for multiple channels. The channel changes depending on the major release of the snapshot. ie. 2.0 vs 2.1
• Add DOWNSTREAM support to MCE upgrade.sh

Motivation for the change:

• Installing new major releases
• Upgrade downstream releases

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gurnben, jnpacker

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