Fix to use right device for DALI iterator
Fix to use right device for DALI iterator

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