Caffe2: allow nets that don't use all input in net.ClonePartial
Caffe2: allow nets that don't use all input in net.ClonePartial

Summary: Caffe2: allow nets that don't use all input in net.ClonePartial

Differential Revision: D5535564

fbshipit-source-id: 0ec8fb3ade4d7d6cd4a702c9c265d9c77f27a627

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