fix android build
fix android build

Summary:
The most recent diff from Andrey had a tiny bug that triggered an error in Android.
Closes https://github.com/caffe2/caffe2/pull/543

Differential Revision: D5040516

Pulled By: Yangqing

fbshipit-source-id: d7b11b509a20b8b5e33db74dd383b55f43608c8f

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