That's a lot of races! Well, 4 of them were all related, but the fixes to
them had to be made in two different places.

Hopefully that's all the v6 races fixed. I've been finding these races by
inspection, who knows if I missed some. Anyway, I'm now down to one todo
item left on the v6 sprint. Gonna take a break for a couple days before
tackling it.

This work is supported by the NSF-funded DataLad project.
