inputselector: Ensure that events are pushed first on active pad
Making it less random and fixing a race in a GES test where we have as pipeline:
videotestsrc ! output-selector name=s ! input-selector name=i s. ! timecodestamper ! i.
which we seek, leading to the seek reaching the video testsrc without going through the timecodestamper and generating a buffer even before timecodestamper gets the seek which means that its internal state is wrong compared to the datastream it gets and attaches wrong timecode metas.