Faster version for RowWiseSparseAdagradOp
Faster version for RowWiseSparseAdagradOp

Summary: Move common operation out of loop.

Reviewed By: dzhulgakov

Differential Revision: D5962894

fbshipit-source-id: e4f8a5406c870958215cbc1fd366fa87bc381471

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