[CUDA][cuBLAS] Check if a context is present when grabbing a cuBLAS handle (#120131)
cuBLAS has indicated that certain kernels will transition to using the driver API over the CUDA runtime API, which we've observed to break existing tests (e.g., DataParallel) that use multithreading and may not eagerly grab a context via `cudaSetDevice`.
CC @Aidyn-A @ptrblck
Co-authored-by: Aidyn-A <31858918+Aidyn-A@users.noreply.github.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120131
Approved by: https://github.com/atalman
