Merge pull request #5983 from jfsiebel/akka-add-sync-voice-user

...bluebutton/core/apps/voice/SyncGetVoiceUsersMsgHdlr.scala

.../scala/org/bigbluebutton/core/apps/voice/VoiceApp2x.scala

...n/scala/org/bigbluebutton/core/running/MeetingActor.scala

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

.../scala/org/bigbluebutton/common2/msgs/VoiceConfMsgs.scala

...html5/imports/api/users/server/modifiers/addDialInUser.js

...utton-html5/imports/api/users/server/modifiers/addUser.js

...ton-html5/imports/api/voice-users/server/eventHandlers.js

.../imports/api/voice-users/server/handlers/joinVoiceUser.js

...ml5/imports/api/voice-users/server/handlers/voiceUsers.js