When hooking vop_rename_post(), the preexisting dst vnode will be
unlocked. But, we need to invoke VOP_GETATTR on it in vn_inotify() to
check its link count.
In inotify_unlink_watch_locked(), the vnode interlock is not held, so
don't use vn_irflag_unset_locked().
Fixes: f1f230439fa4 ("vfs: Initial revision of inotify")