Fix typo in warning in data_parallel_model
Fix typo in warning in data_parallel_model

Summary: Closes https://github.com/caffe2/caffe2/pull/1219

Differential Revision: D5898077

Pulled By: Yangqing

fbshipit-source-id: 7ee726ef3399a350a36e77093cbad0f70f8f3dce

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