fsnotify: move events should indicate the event was on a child

fsnotify tells its listeners explicitly when an event happened on the given
inode verses on the child of the given inode.  (see __fsnotify_parent)
However, the semantics of fsnotify_move() are such that we deliver events
directly to the two parent directories in question (old_dir and new_dir)
directly without using the __fsnotify_parent() call.  fsnotify should be
adding FS_EVENT_ON_CHILD for the notifications to these parents.

Signed-off-by: Eric Paris <eparis@redhat.com>