btrfs: test btrfs send after swapping directory names differently

btrfs: test btrfs send after swapping directory names differently

Test btrfs incremental send after renaming and moving directories around in a
way that ends up making a directory have different dentries with the same name
but pointing to different inodes in the parent and send snapshots, and also
inverting the ancestor-descendent relationship between one of those inodes and
some other inode.

Cases like this made an incremental send enter an infinite lopp when building
path strings, leading to -ENOMEM errors when the path string reached a length
of PATH_MAX.
This issue was fixed by the following linux kernel btrfs patch:

  Btrfs: incremental send, check if orphanized dir inode needs delayed rename

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>