Fix Exporting RNN/LSTM's Initial State (h0/c0) to ONNX
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/22813
Reviewed By: hl475
Differential Revision: D16275791
Pulled By: houseroad
fbshipit-source-id: 6e2259e84e1f5a674daabcbe0df99b1360ed2b35
