We are not storing plan data in Mistral any longer, all of it is now
in the plan-environment.yaml file in Swift.
Change-Id: I3e8b760b53e8554c2e6b80f198e2983cb56bbad9
Depends-On: Ieedecf92113142e43925131dcbccc4c0cd5b1a18
Implements: blueprint stop-using-mistral-env