fix: Fix requested output deleting extra outputs (triton-inference-server#390)

* fix: Hold GIL when deleting numpy array

* chore: setting py obj to None may not destruct the object

Author: kthui

src/pb_stub.cc

@@ -1032,9 +1032,9 @@ Stub::~Stub()
 
   {
     py::gil_scoped_acquire acquire;
-    async_event_loop_ = py::none();
-    background_futures_ = py::none();
-    model_instance_ = py::none();
+    py::object async_event_loop_local(std::move(async_event_loop_));
+    py::object background_futures_local(std::move(background_futures_));
+    py::object model_instance_local(std::move(model_instance_));
   }
   stub_instance_.reset();
   stub_message_queue_.reset();

src/pb_tensor.cc

@@ -503,6 +503,14 @@ PbTensor::~PbTensor() noexcept(false)
 {
   pb_memory_.reset();
   DeleteDLPack();
+
+#ifdef TRITON_PB_STUB
+  {
+    py::gil_scoped_acquire acquire;
+    py::array numpy_array_local(std::move(numpy_array_));
+    py::array numpy_array_serialized_local(std::move(numpy_array_serialized_));
+  }
+#endif
 }
 
 const std::string&