Add test to backward sole array node
Add test to backward sole array node

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