- Make the srt_epoll_wait loops more uniform. - Error only via GError when possible; let the element send the error message. Avoids a second error message. - Return 0 when cancelled. Avoids an error message from the element. - Don't send an error message from send_headers when we're a server sink. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3156>