[shape inference] adding a new flag to the struct
Summary: Adding a new flag shape_is_set to the structs for shape inference on in-place op to prevent duplicated inference.
Test Plan:
buck test mode/opt-clang caffe2/caffe2/opt:bound_shape_inference_test
buck test mode/opt-clang caffe2/caffe2/fb/opt:shape_info_utils_test
Reviewed By: ChunliF
Differential Revision: D24134767
fbshipit-source-id: 5142e749fd6d1b1092a45425ff7b417a8086f215
