Remember Me allows user to be logged in twice

To reproduce:

• With one browser, log in, and activate "Remember me".
• With another browser, log in with the same user.

Expected behavior: The user is logged out in the first browser
Actual behavior: Both users are still logged in and can browse/edit the same document simultaneously/etc.

Alternative reproduction path:

• With one browser (e.g. Chrome), log in with "Remember me" activated
• Close the browser.
• With another browser (e.g. Firefox), log in with "Remember me" activated
• Open the first browser again, and go to the CMS

Expected behavior: One of the browsers sessions expire
Actual behavior: Both sessions are still active and can be used