largefiles: handle that a found standin file doesn't exist when removing it I somehow ended up in a situation where hg crashed on an unlink I introduced in 328545c7d8a1. I don't know how it happened and can't reproduce it. It seems like it only can happen when the file is removed between the time of check in a working directory context walk that finds a standin file, and the time of use when we try to remove it because the corresponding largefile doesn't exist. But better safe than sorry: replace the plain unlink with unlinkpath with ignoremissing=True. That will also remove remaining empty directories, which arguably is more correct.