MDS: scrub: forward scrub reports missing backtraces on new files as damage
It appears that running a recursive repair scrub_path results in reports of MDS damage on files that are new enough their backtraces haven't been persisted yet, even though
1) the backtrace isn't expected to be there yet, and
2) it then happily wrote it down correctly. (Well, I didn't check, but I presume.)
This is silly. Fix it!