bigbluebutton/bigbluebutton — pull request #438 by ritzalam (2014-11-20 18:56:17+00:00)
Title:  - for some reason we either (a) get duplicate events for user join from...

... FS or (b) FS-ESL isn't handling

the event properly. This results in duplicate entries on the user's list when user calls in from the
phone. Check if a voice user with the same id is already in the voice conference and ignore the second
event.