buildinfos.d.n: fix logic for old buildd files

Newer buildinfo files form the buildds are named -buildd.buildinfo and
preferred as fixed in c5bd2cdd. Before that they where renamed .0 or .1
if the file already existd. This makes sure those are preferred as well.

Signed-off-by: Holger Levsen <holger@layer-acht.org>