Use hypothesis to to control the rand seed (#36717)
Summary:
This will increase the test coverage.
More tests to enable:
```
test_fc_nnpi_fp16.py
test_op_nnpi_fp16.py
test_batchmatmul_nnpi_fp16.py
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36717
Reviewed By: hyuen
Differential Revision: D21061269
Pulled By: yinghai
fbshipit-source-id: 99277db8ff23f0f4e679f7b8955cfa305916e7a7
