[single_controller, ray] fix: shut ray down after initializes it (#3317)

### What does this PR do?

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Reference related GitHub issues and PRs that help with the review.

To prevent Ascend NPU TBE errors caused by resource leakage, ensure that
ray.shutdown()is explicitly called after initializing Ray with
ray.init().

Address the first issue in
https://github.com/volcengine/verl/issues/3316

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Co-authored-by: lantian7 <liuchun22@huawei.com>

recipe/dapo/main_dapo.py

@@ -46,19 +46,23 @@ def run_ppo(config) -> None:
         print(f"ray init kwargs: {ray_init_kwargs}")
         ray.init(**OmegaConf.to_container(ray_init_kwargs))
 
-    if (
-        is_cuda_available
-        and config.global_profiler.tool == "nsys"
-        and OmegaConf.select(config.global_profiler, "steps") is not None
-        and len(OmegaConf.select(config.global_profiler, "steps")) > 0
-    ):
-        nsight_options = OmegaConf.to_container(
-            config.global_profiler.global_tool_config.nsys.controller_nsight_options
-        )
-        runner = TaskRunner.options(runtime_env={"nsight": nsight_options}).remote()
-    else:
-        runner = TaskRunner.remote()
-    ray.get(runner.run.remote(config))
+    try:
+        if (
+            is_cuda_available
+            and config.global_profiler.tool == "nsys"
+            and OmegaConf.select(config.global_profiler, "steps") is not None
+            and len(OmegaConf.select(config.global_profiler, "steps")) > 0
+        ):
+            nsight_options = OmegaConf.to_container(
+                config.global_profiler.global_tool_config.nsys.controller_nsight_options
+            )
+            runner = TaskRunner.options(runtime_env={"nsight": nsight_options}).remote()
+        else:
+            runner = TaskRunner.remote()
+        ray.get(runner.run.remote(config))
+    finally:
+        if ray.is_initialized():
+            ray.shutdown()
 
 
 @ray.remote(num_cpus=1)  # please make sure main_task is not scheduled on head