Sets the correct start padding value when an edit list is present.

A new fate test is added, fate-mov-440hz-10ms, to ensure this is
handled correctly.
Signed-off-by: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Sasi Inguva <isasi-at-google.com@ffmpeg.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>