Remove the return when encountering invalid packet.
Also, log more sparesely.
Proper error returns from util so that we can selectively drop packets
based on error type, for example SSRC mismatches are okay type of thing.
* Validate RTP packets.
Check version, payload type (if available) and SSRC (if available)
and drop bad packets. And let repair mechanisms take effect for those
packets.
* address data race reported by test
* fix an unlock and test packets