Fixes the net-rewriting pipeline for model with rowwise adagrad
Fixes the net-rewriting pipeline for model with rowwise adagrad

Summary: Model with rowwise RMSProp does not work in net-rewriting pipeline (fbl 29841194). This diff solves the issue by changing the way Slice op is used in the model and adds a rule to `parallelize.py` to cover for needed cases.

Reviewed By: azzolini

Differential Revision: D6096022

fbshipit-source-id: c4f615b2ba99da9f77a1d49c9fb898e0e59401f8

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