switch to a new sync message on html5 only redis channel

...ore/apps/whiteboard/SyncWhiteboardAccessRespMsgHdlr.scala

.../org/bigbluebutton/core2/FromAkkaAppsMsgSenderActor.scala

.../main/scala/org/bigbluebutton/common2/msgs/UsersMgs.scala

...scala/org/bigbluebutton/common2/msgs/WhiteboardMsgs.scala