set track.scanned the very last thing we do
set track.scanned the very last thing we do

because the way we update the track sqlalchemy runs 3 different queries
so before an artist would have been set scanned could have already been
set to true which led to race conditions in upload (at least).

opmuse/opmuse,opmuse/opmuse,opmuse/opmuse,opmuse/opmuse