This method is independent of how the extractor works, unlike the
previous method. Now on a extractor failure, the miner does:

1) Pause itself
2) Wait for all pending extractor requests to finish
3) Accumulate all failed extractions on a list
4) Run through that list items, extracting again one file at a time.
5) Resume itself

Conflicts:

	src/miners/fs/tracker-miner-files.c