Update return codes in PyTest to properly error out if tests fail (#5122)
Update PyTest return codes to better reflect the [documented exit
codes](https://docs.pytest.org/en/7.1.x/reference/exit-codes.html). This
was causing issues in the nv-inference test.
Build with nv-inference with just the returncode changes, showing that
as [now
failing](https://github.com/microsoft/DeepSpeed/actions/runs/7880331865/job/21502182220)
with CUDA OOM errors.
Sample previous passing build
[here](https://github.com/microsoft/DeepSpeed/actions/runs/7719051411/job/21041568991).