generic: test fsync after adding a link and moving other inode

generic: test fsync after adding a link and moving other inode

Test that if we create a hard link for a file F in some directory A,
then move some directory or file B from its parent directory C into
directory A, fsync file F, power fail and mount the filesystem, the
directory/file B is located only at directory A and both links for
file F exist.

This test is motivated by an issue found in btrfs which is fixed by the
following patch for the linux kernel:

  Btrfs: fix for incorrect directory entries after fsync log replay

Tested against ext3/4, xfs, reiserfs and f2fs.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>