Add missing security fixture to solve issue with non-admin users

The `security` fixture was missing, causing a non-admin user to get infinite redirect loop while he/she tries to open a map.

Now pre-generated maps have a security model which allows everyone is registered to view them and the GEM account (and all admins) to edit them.

Fixes https://bugs.launchpad.net/oq-platform/+bug/1401247