btrfs: test incremental send swapping location of a directory with a file

btrfs: test incremental send swapping location of a directory with a file

Test that an incremental send operation succeeds, and produces the
correct results, after renaming and moving around directories and files
with multiple hardlinks, in such a way that one of the files gets the old
name and location of a directory and another name (hardlink) with the old
name and location of another file that was located in that same directory.

This currently fails on btrfs but is fixed by a kernel patch with the
following subject:

  "btrfs: send: fix invalid path for unlink operations after parent orphanization"

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>