xfs_repair: adjust keep_fsinos to handle metadata directories

xfs_repair: adjust keep_fsinos to handle metadata directories

In keep_fsinos, mark the root of the metadata directory tree as inuse.
The realtime bitmap and summary files still come after the root
directories, so this is a fairly simple change to the loop test.

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