Initialize CUDA context in graph shutdown probe (NVIDIA#2375)

The subprocess does not inherit the pytest init_cuda fixture context. Set its device current before adding the host callback node so the probe reaches the shutdown-cleanup behavior it is intended to test.

Author: rwgk

cuda_core/tests/graph/test_graph_definition_lifetime.py

@@ -443,7 +443,8 @@ class Callback:
             def __call__(self):
                 pass
 
-        Device()
+        device = Device()
+        device.set_current()
         graph = GraphDefinition()
         graph.callback(Callback())
         """