Fix repair packets not received by FEC stream
2 fixes :
- change payload type number assignement for special payloads and flexfec: search if a number has already been assigned
- reset the profile of the principal RTP session to the FEC session when updated, and use the receive payload type instead of the profile to identify the session to assign a SSRC in the bundle.
The test "Asymmetrical video call with flexfec starts with video" in test suite "video call" has been added to check that the repair packets of the FEC are correctly send to the FEC session during an asymetrical video start.
Edited by Flore Harlé