Fix batch_isend_irecv tests for err case (#63112)
Summary:
- `batch_isend_irecv` returns a list of requests instead of a single request
- remove some unused variables
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63112
Reviewed By: pbelevich, wayi1, fduwjj
Differential Revision: D30921265
fbshipit-source-id: e2075925172805d33974ef0de6fb631bdf33b5ea
