System settings tiles not consulted when running the development server

[jacobtylerwalls]

As discussed in #11660 and #11697, the documented inheritance order for settings configurable through the UI is that they trump everything, including python settings modules.

However, this only works correctly when running a WSGI application, not in dev, since wsgi.py calls update_from_db(), and nothing in the dev server does.

A first attempt at fixing this that didn't account for setup_db.