Current Adoption docs assume that we're adopting within the same release. Let's refactor the docs workflow towards the "FFUdoption" variant that we'll be aiming for - FFU and Adoption converged into one thing. That means mainly getting rid of "adoptionRedirect" for MariaDB, and reordering things (e.g. Keystone needs to be started after MariaDB import, not before, as it will never connect to external MariaDB).