Fix multi gpu mnist exmaple
Fix multi gpu mnist exmaple

niboshi/chainer,jnishi/chainer,okuta/chainer,chainer/chainer,chainer/chainer,cupy/cupy,ronekko/chainer,ysekky/chainer,keisuke-umezawa/chainer,cupy/cupy,pfnet/chainer,hvy/chainer,kiyukuta/chainer,niboshi/chainer,keisuke-umezawa/chainer,jnishi/chainer,ktnyt/chainer,okuta/chainer,cupy/cupy,ktnyt/chainer,cupy/cupy,anaruse/chainer,kashif/chainer,wkentaro/chainer,delta2323/chainer,niboshi/chainer,hvy/chainer,okuta/chainer,ktnyt/chainer,tkerola/chainer,niboshi/chainer,wkentaro/chainer,aonotas/chainer,wkentaro/chainer,jnishi/chainer,rezoo/chainer,chainer/chainer,ktnyt/chainer,hvy/chainer,okuta/chainer,jnishi/chainer,wkentaro/chainer,keisuke-umezawa/chainer,hvy/chainer,chainer/chainer,keisuke-umezawa/chainer