This was disabled in commit 61ccf95004,
because only the assistant used them, and they were clutter. But, now
--failed also uses them.
Remove the failure log files after successful transfers. Should avoid
most of the clutter problems.
Commit 61ccf95004 mentions a subtle behavior
change, which has now been reverted:
There is one behavior change from this. If glacier is being used, and a
manual git annex get --from glacier fails because the file isn't available
yet, the assistant will no longer later see that failed transfer file and
retry the get.
f461bcae4b