xfs_io: adapt parent command to new parent pointer ioctls

xfs_io: adapt parent command to new parent pointer ioctls

For ages, xfs_io has had a totally useless 'parent' command that enabled
callers to walk the parents or print the directory tree path of an open
file.  This code used the ioctl interface presented by SGI's version of
parent pointers that was never merged.  Rework the code in here to use
the new ioctl interfaces that we've settled upon.  Get rid of the old
parent pointer checking code since xfs_repair/xfs_scrub will take care
of that.

(This originally was in the "xfsprogs: implement the upper half of
parent pointers" megapatch.)

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>