Set listenOnly to false when user left voice

The message/event UserLeftVoiceConfToClientEvtMsg is used when user leaves mic and listenonly, but it only sets to false the 'voiceJoined' (which represents the <hasVoiceVoiceJoined> property in BBB's XML API.
We now also set to false the 'listeningOnly' (which represents the <isListeningOnly> property in BBB's XML API). Setting both to false is not a problem, once 'MIC' and 'ListenOnly' states are mutually exclusives
Fixes #10852