ffprobe: fix format section XML validation

It was broken since 2186a7e547fdda716138444c8345ce8b823f2d4a.
ffprobe: show probe_score in the format section

Should address trac ticket #2621.
fate: update fate tests after master:291ad12ea2d1: ffprobe: show probe_score in the format section

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>