Fast-forward upgrades for tripleo

Fast-forward upgrades are upgrades that move an environment from release `N` to `N+X` in a single step, where `X` is greater than `1` and for fast-forward upgrades is typically `3`. This blueprint outlines how such upgrades can be orchestrated by TripleO between the Newton and Queens releases.

Virtual instance rescue with stable disk devices for OpenStack Compute (nova)

This will provide the ability to indicate that the rescue disk image should be attached as a transient disk device (ie USB stick), so that existing storage attached to an instance doesn't change its device address during rescue mode.