fix using `var` without eps to with eps.
fix using `var` without eps to with eps.

niboshi/chainer,wkentaro/chainer,okuta/chainer,hvy/chainer,niboshi/chainer,niboshi/chainer,hvy/chainer,pfnet/chainer,chainer/chainer,chainer/chainer,okuta/chainer,chainer/chainer,wkentaro/chainer,okuta/chainer,okuta/chainer,hvy/chainer,niboshi/chainer,wkentaro/chainer,wkentaro/chainer,chainer/chainer,hvy/chainer