[RB] 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` user (and all the admins) to edit them.

How to test:
1) With current master create a normal user, login with it and try to open a pre-created map. You'll get an infinite redirects loop error
2) With this branch try the same, you'll get the map

Fixes https://bugs.launchpad.net/oq-platform/+bug/1401247