walk::scan_root enqueued an ExtractMetadata and a Thumbnail job for every
image it inserted or found changed. No handler claims either kind. The
walk is only reachable from the scan_local example today, so no real
catalog holds these rows, but it is the same leftover the remote scan
carried (#73) and it is what a local library would inherit.
Both debts are already recorded where their consumers look: an inserted
or changed image is written at metadata_state 1, which is the metadata
sweep's work list, and the thumbnail store answers for itself.
The tests that used job rows as the measure of "this image owes work"
now read metadata_state, which is the record the sweep actually uses;
the no-requeue test marks the first image read before the second scan,
so it still proves an unchanged neighbour is not put back in debt.
Refs #73
dtourolle
5fcd3752d7