This reverts commit ff11a1a8a0c685d2edd0e06c0071cbb94f2cb663.
It can't be assumed that all buffers in a buffer list have the same SSRC or
are RTP or RTCP only. It has to be checked for every single buffer, and one
basically has to do the processing that is done by the default chain_list
implementation.
88f85f6595