The torture tests were looking for the anchor tag within each
button. However, that anchor could get blown away from a react
re-render. So instead, expose a way for the torture tests
to find the root node of the button.
config.disableDesktopSharing - when set to false will disable desktop
sharing
interfaceConfig.DESKTOP_SHARING_BUTTON_DISABLED_TOOLTIP - when value is
assigned, will not hide the desktop sharing button completely, but show
as disabled with this value used as the tooltip text.
Audio only mode can be used to save bandwidth. In this mode local video is muted
and last N is set to 0, thus disabling all remote video.
When this mode is enabled avatars are shown.