Missing tile in track count increase

[burak-58]

Cause: If the mapSubtrackState in WebRTCClient doesn't contain the selfTrackId, current active tracks count calculation (mapSubtrackState -2) becomes wrong. Then we don't increase the number of tracks as desired and miss one track.

On possible solution: adding selfTrackId into mapSubtrackState when subtrackPoller calls addTrackOnTheFly.