xfs_db: use an empty transaction to try to prevent livelocks in path_navigate

xfs_db: use an empty transaction to try to prevent livelocks in path_navigate

A couple of patches from now we're going to reuse the path_walk code in
a new xfs_db subcommand that tries to recover directory trees from
old/damaged filesystems.  Let's pass around an empty transaction to try
too avoid livelocks on malicious/broken metadata.  This is not
completely foolproof, but it's quick enough for most purposes.

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