This (and the `unlink` later on) is (mostly in theory, since nobody is supposed to create or remove any files in Arakoon dirs except for the running process) a [TOCTOU](http://en.wikipedia.org/wiki/Time_of_check_to_time_of_use) bug. There's a `safe_unlink` utility in `Node_cfg` which works around this. Consider moving that to `File_system` and use it?