res_rtp_asterisk: Free payload when error on insertion to data buffer

res_rtp_asterisk: Free payload when error on insertion to data buffer

When the ast_data_buffer_put rejects to add a packet, for example because
the buffer already contains a packet with the same sequence number, the
payload will never be freed, resulting in a memory leak.

The data buffer will now return an error if this situation occurs
allowing the caller to free the payload. The res_rtp_asterisk module
has also been updated to do this.

ASTERISK-28826

Change-Id: Ie6c49495d1c921d5f997651c7d0f79646f095cf1