* upstream/master: (26 commits)
  cudnn 7 upgrade with spatialBN fix (pytorch#11291)
  Ignore FuseGraph Call on Windows (pytorch#11015)
  defer resolution of mkl to a cmake wrapper library (pytorch#11298)
  Cleanup dependency of distributed flags (pytorch#11221)
  Move minimal wrapdim functionality to core, remove THTensor include i… (pytorch#11283)
  Change includes from ATen/Storage.h to ATen/core/Storage.h (pytorch#11217)
  Fix scalar tensor assert in fusion compiler (pytorch#10952)
  Add dead code elimination pass (pytorch#10101)
  Distributed Data Parallel CPU module for C10D (pytorch#11168)
  Back out "[pt1][tensor] Add strides to caffe2::Tensor"
  Fix conv gradient conversion (pytorch#11312)
  Bag of clang tidy fixes for torch/csrc/ and torch/csrc/autograd (pytorch#11050)
  Sparse tensor printing; add NotImplemented autograd fn (pytorch#10181)
  Add convertToCaffe2Proto to python API
  fix doc for functional.dropout* (pytorch#10417)
  typo fix Tranpose2D -> Transpose2D (pytorch#11281)
  Remove THFinalizer
  Forward declarations of needed curand functions (pytorch#10911)
  nomnigraph - simplify core graph API and test (pytorch#11256)
  Small fixes to cppdocs for sync script (pytorch#11300)
  ...

Summary:
Pull Request resolved: pytorch#11256

- in deleteNode method, remove optional deleteEdge flag as it's not used
- in deleteEdge method, remove optional removeRef flag as it's not used
- in replaceNode method, remove optional newHead_ parameter as it's not used - also simplifying the implementation by just calling replaceInEdges and replaceOutEdges
- remove importNode & importEdge as they're not in used
- add getEdgeIfExists that is like getEdge() but returns nullptr instead of throwing when the edge does not exist
- reduce verbosity in the basic graph unit test and add more test cases for ReplaceEdges

Differential Revision: D9650913

fbshipit-source-id: 6c18b37bef0d2abe1b57fb4fc47bfdbcee387694