Master user switch doesn't work with role change or deletion

We should find a better way to handle what happens to the Jetpack connection and the master user when that user gets deleted or has a role change.

@dereksmart and I have spoken about handing off the connection to another connected admin (if there is only one connected admin remaining, otherwise they should be presented with the option to choose the new primary).

However right now when a connected admin is the only connected admin and their account gets changed to a lower role or they are deleted the connection seems to remain in place but that is not the case.

No files or tests are named. Start by tracing how the Jetpack connection and master user are handled when a connected admin is deleted or changed to a lower role. Done means the connection remains valid and is handed to the only remaining connected admin or the user can choose a new primary when multiple admins remain.

Written by the indexing model from the issue text.