btrfs: incremental send after moving directories around

btrfs: incremental send after moving directories around

Test that an incremental send operation works after doing radical
changes in the directory hierarchy that involve switching the inode
that directory entries point to.

This test exercises scenarios used to fail in btrfs and are fixed by
the following patches for the linux kernel:

 "Btrfs: send, fix failure to move directories with the same name around"
 "Btrfs: incremental send, fix invalid paths for rename operations"

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