Past chat sessions can be made available for everyone to view

This test requires a chat with saved past chat sessions. Check that student permission 'Read chat logs mod/chat:readlog' set to Prevent.

1. Login as a teacher, update a chat activity and set 'Everyone can view past sessions' to Yes.
2. Login as a student, access the chat and check that past chat sessions can be viewed via the 'View past chat sessions' link.
3. Login as a teacher, update the chat activity and set 'Everyone can view past sessions' to No.
4. Check that past chat sessions can be viewed (as a teacher) via the 'View past chat sessions' link.
5. Login as a student, access the chat and check that there is no longer a 'View past chat sessions' link.