Test only if the model was trained on single GPU for accurate results.
# Changelog
- Revert previous code that constructs a trainer on one GPU to evaluate results. The code is misleading because the torch environment is still distributed, and all processes run the code
- From now on, test only if the model was trained on a single GPU with no ddp.

Signed-off-by: smajumdar <titu1994@gmail.com>