Participation report is not correctly implemented

Tested with 2.4 master and it seems to work correctly.

Ways to reproduce the issue:

• Enrol a couple of users in a course under students or teacher role (at least one each)

• In turn use the bigbluebutton activity (join a meeting)

• Go to the course participation report (in the cog / More/ Reports/ Course participation or report/participation/index.php?id=<courseid>)

• Select the bbb activity in the drop down

• Check that both teachers and student have their participation indicated (we should have some action indicated in the All actions columns)