[3rdparty] fix redundant process group destroy for ray (#7395)

* fix redundant process group destroy for ray

* Update tuner.py

---------

Co-authored-by: hoshi-hiyouga <hiyouga@buaa.edu.cn>

src/llamafactory/train/tuner.py

@@ -38,6 +38,7 @@ from .trainer_utils import get_ray_trainer, get_swanlab_callback
 
 
 if is_ray_available():
+    import ray
     from ray.train.huggingface.transformers import RayTrainReportCallback
 
 
@@ -77,6 +78,9 @@ def _training_function(config: dict[str, Any]) -> None:
     else:
         raise ValueError(f"Unknown task: {finetuning_args.stage}.")
 
+    if is_ray_available() and ray.is_initialized():
+        return  # if ray is intialized it will destroy the process group on return
+
     try:
         if dist.is_initialized():
             dist.destroy_process_group()