Init comm_nonblocking_ when creating AutoNcclGroup (#99679)
A quick, trial fix for #99677.
My guess is that when the code instantiates an `AutoNcclGroup` object, it comes with an uninitialized random value for member `comm_nonblocking_`. Then `if (comm_nonblocking_)` evaluates to true, and `NCCL_CHECK_TIMEOUT` triggered.
This change is safe (and needed) anyway whether it indeed fixes #99677.
Cc @eqy
Pull Request resolved: https://github.com/pytorch/pytorch/pull/99679
Approved by: https://github.com/eqy, https://github.com/awgu
