In RtpDataLoadable.load, the second UDP data source is opened on the port we
specify. If the port is already in use, a BindException is thrown.
#minor-release
PiperOrigin-RevId: 371319522
Previously loadingFinished will never be set to true because it started in
false, and we are and'ing it with `canceled`.
#minor-release
PiperOrigin-RevId: 370662456