Make sure that we delete devices whenever a user is logged out due to any of
the following situations:
* /logout
* /logout_all
* change password
* deactivate account (by the user or by an admin)
* invalidate access token from a dynamic module
Fixes#2672.
Non-functional refactoring to move set_password. This means that we'll be able
to properly deactivate devices and access tokens without introducing a
dependency loop.
Dirk Klimpel