In RTSP 2.0, they started recommending that clients use an
empty SET_PARAMETER request as the preferred keep-alive mechanism
as all cameras must support that method. It also works
for RTSP 1.0, so use it as the preferred method unconditionally.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/9577>
c086c83ac4