title: ConfBridge: end up conference when admin user exit
body: <p>I am doing something about ConfBridge these days.
  I used "confbridge kick  all" to end the conferences when admin user exit, but the others in the conference will hear "you have been kick out from this conference.". it is not a good way to end a conference.
  Is there any configure or command which can set that conference will end up when the admin user exit the conference? </p>