Fix ChainerX fallback for replaced optimizer state
Fix ChainerX fallback for replaced optimizer state

wkentaro/chainer,chainer/chainer,niboshi/chainer,keisuke-umezawa/chainer,okuta/chainer,wkentaro/chainer,keisuke-umezawa/chainer,okuta/chainer,hvy/chainer,niboshi/chainer,hvy/chainer,niboshi/chainer,wkentaro/chainer,niboshi/chainer,hvy/chainer,keisuke-umezawa/chainer,okuta/chainer,keisuke-umezawa/chainer,chainer/chainer,tkerola/chainer,pfnet/chainer,wkentaro/chainer,hvy/chainer,okuta/chainer,chainer/chainer,chainer/chainer