xfs: fix online repair block reaping

These patches fix a few problems that I noticed in the code that deals
with old btree blocks after a successful repair. First, we clarify how
the reaping function works w.r.t. bitmap lifetimes.  Next we fix a bug
where we could incorrectly invalidate old btree blocks if they were
crosslinked.  Finally, we convert the reap function to use EFIs so that
we can delete blocks without overloading a transaction.
-----BEGIN PGP SIGNATURE-----
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=d9Rm
-----END PGP SIGNATURE-----