Merge pull request #5784 from capilkey/2.0-screenshare-sound-n-lock-fix

...tton/modules/screenshare/assets/sounds/ScreenshareOff.mp3

...utton/modules/screenshare/managers/ViewerWindowManager.as

...odules/screenshare/managers/WebRTCPublishWindowManager.as

...modules/screenshare/managers/WebRTCViewerWindowManager.as

...screenshare/view/components/ScreensharePublishWindow.mxml

...reenshare/view/components/WebRTCDesktopPublishWindow.mxml

...g/bigbluebutton/modules/users/services/MessageReceiver.as

.../bigbluebutton/modules/users/views/MediaItemRenderer.mxml