Fix backward compatibility bug for cnn model helper arguments
Fix backward compatibility bug for cnn model helper arguments

Summary:
For new trained models passing kernels=2*[kernel] and using old code for
inference that will not work because (kernels) argument isn't supported and
we are not passing kernel.

Reviewed By: salexspb

Differential Revision: D4888795

fbshipit-source-id: 1649b073c4e1da1d59da9cea581b4dcab6dbaf5c

sf-wind/caffe2,sf-wind/caffe2,pietern/caffe2,Yangqing/caffe2,pietern/caffe2,davinwang/caffe2,pietern/caffe2,pietern/caffe2,xzturn/caffe2,davinwang/caffe2,pietern/caffe2,sf-wind/caffe2,xzturn/caffe2,bwasti/caffe2,bwasti/caffe2,davinwang/caffe2,xzturn/caffe2,xzturn/caffe2,Yangqing/caffe2,davinwang/caffe2,xzturn/caffe2,Yangqing/caffe2,davinwang/caffe2,bwasti/caffe2,sf-wind/caffe2,caffe2/caffe2,Yangqing/caffe2,sf-wind/caffe2,bwasti/caffe2,bwasti/caffe2,Yangqing/caffe2