Wiki 2.0 does not respect 'visible groups' functionality.

The wiki tool no longer works for visible groups.

To reproduce:

1. Set up some groups and enrol some students in the course & groups.
2. Set up a new wiki and set to 'visible groups' mode.
3. Log in as one of the students.
4. Edit a page in your group's wiki - no problem, I can edit it, which is good.
5. Change the group in the drop-down to show another group page.
=> You can edit this other group's page, even though its a Visible Group - very NOT GOOD as it should only allow you to view, but not edit, as it did in Moodle 1.9.