validation and training loops run the partial dataset (#1192)
validation and training loops run the partial dataset (#1192)

* auto_add_sampler() fix

* auto_add_sampler() fix

Co-authored-by: seth <25a3b6cc85a8cde49f8b0f9aa21c050bc04072d4@duckpapa.com>
williamFalcon/pytorch-lightning,williamFalcon/pytorch-lightning