Fix BN problem, it works with copy().
Fix BN problem, it works with copy().

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