After a flushing seek, rtspsrc doesn't reset the last_ret value for streams, so might immediately shut down again when it resumes pushing buffers to pads due to a cached `GST_FLOW_FLUSHING` result Prevent a stored flushing value from immediately stopping playback again by resetting pad flows before (re)starting playback. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6137>