ext4: fix possible double unlock when moving a directory

Fixes: 0813299c ("ext4: Fix possible corruption when moving a directory")
Link: https://lore.kernel.org/r/5efbe1b9-ad8b-4a4f-b422-24824d2b775c@kili.mountain


Reported-by: Dan Carpenter <error27@gmail.com>
Reported-by:  <syzbot+0c73d1d8b952c5f3d714@syzkaller.appspotmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>