Fixes #932 delete user sessions

This is a bugfix.

## Problem
When a user is changed to "non-active", he still can move around in the CMS if he was already logged in.

## Solution
The sessions for this user will be removed immediately, so the user is logged out immediately.

## Test yourself
Open two browsers, in the one you log in as "GOD" user, in the other one you log in as the "user" that will be de-activated. Use GOD to disable "active". Now go to the other browser and refresh an you will see that you are logged out.

Fixes #932