Fix bench with media pip / background running

When starting the benchmark with a third app media running in pip, there will be the overlap of the pip window on the first sample played. In the case of VLC-Android, in pip or background, the media playing is restarted, and not the one wanted by the benchmark. This only affects the first sample played. After testing several fixes, this is the ugly solution that works. Running a dummy first sample that isn't used in the results, before playing all the benchmark tests normally.