Fix for #1911: don't assume SQLite in setup.

In migrating our ansible scripts to use this setup command (see https://github.com/fle-internal/ansible-playbooks/pull/17), it became clear that our setup script assumes a SQLite back-end.

One core goal for KA Lite is to make the product database engine-agnostic.  This PR does that! :)

Testing:
* Tested sqlite clean and upgrade installs.  Both work as previously.