Half billion tries for a HAMMER2 bug

I’m pulling a quote off of IRC to show some of the testing on HAMMER2, specifically as the background for this commit:

14:22 <@dillon_> ^^^ hammer2 bug, could reproduce it around once a day doing a continuous rm -rf on hardlinked snapshots. reproduced about once every 500 million directory entries or so

I am somewhat tickled by the notion that you might have a problem after deleting half a billion directory entries.