Fix minor bug related to pinned memory allocator
Fix minor bug related to pinned memory allocator

Summary: Came across while reading something. Missing return statement.

Reviewed By: pietern, dzhulgakov

Differential Revision: D4626160

fbshipit-source-id: 4811b9c720510c76d3aadd93cee00f342f6552de

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