downloadbuffer: fix push mode
urisourcebin download=true
is not working atm.
gst-launch-1.0 urisourcebin uri=https://files.desmottes.be/brol/sync-test.mp4 download=true ! fakesink silent=false -v
Best case scenario it does produce buffers but get stuck as EOS
is never sent. Worst cast it's stuck right away forever.
Making it work by fixing a couple of problems in push mode.