fsnotify: Fix bad field name in list iterations

Surprisingly, but

offsetof(inotify_wd_entry, node) == offsetof(fanotify_mark_entry, node)

even though both structures have node field in the middle and the
fields sitting above one are totally different.

So the code works, but ... we're risking :)

Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>