Investigate live testing an upgrade to chef 15 on our chef server

This comes from a proposal in the ~"team::CI/CD & Enablement" meeting about estimating the work to be performed for a chef upgrade, to upgrade our chef server (or a copy of it) to v15.x and gather data in regards to errors, warnings, and the general state of our chef setup in an upgraded environment. Such an experiment should prioritize:

  • Avoiding setting up alarms and especially page calls for the current on-call
  • Have a fast and readily available rollback strategy

/cc @ahanselka @nnelson @devin @cmcfarland @dawsmith