xfs: fixup the metabtree reservation in xrep_reap_metadir_fsblocks

All callers of xrep_reap_metadir_fsblocks need to fix up the metabtree
reservation, otherwise they'd leave the reservations in an incoherent
state.  Move the call to xrep_reset_metafile_resv into
xrep_reap_metadir_fsblocks so it always is taken care of, and remove
now superfluous helper functions in the callers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>