GMS-2015-21: Denial-of-service possibility in logout() view by filling session store

A session can be created when anonymously accessing the django.contrib.auth.views.logout view (provided it wasn’t decorated with django.contrib.auth.decorators.login_required as done in the admin). This allows an attacker to easily create many new session records by sending repeated requests, potentially filling up the session store or causing other users’ session records to be evicted.