Deploy a testing server for system-image updates

A testing server for image based upgrades is different than a staging server.

For a test server, we'll deploy canned updates which can be used to flex the system-image updater. They will look like real updates with real channels, but with canned data, we can test other interesting corner cases (like phased updates) without having to cook real data. We'll also use the testing server as part of the QA plan for system image updates.

We may eventually also need a staging server, but that's a different plan.