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

main/data_buffer.c

@@ -254,7 +254,7 @@ int ast_data_buffer_put(struct ast_data_buffer *buffer, size_t pos, void *payloa
 	AST_LIST_TRAVERSE_SAFE_END;
 
 	if (inserted == -1) {
-		return 0;
+		return -1;
 	}
 
 	if (!inserted) {