Allow 2FA to be setup on first login

Once 2FA is enforced for a user and they have no 2FA setup yet this will
now prompt them with a setup screen. Given that providers are enabled
that allow setup then.

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>
Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>