fix: close write object stream always (#1661)

fix: close write object stream always. 

otherwise Task will remain for long time until GC kills it and it'll
throw this `"Task was destroyed but it is pending!"`

Author: chandra-siri

google/cloud/storage/_experimental/asyncio/async_appendable_object_writer.py

@@ -267,7 +267,8 @@ async def close(self, finalize_on_close=False) -> Union[int, _storage_v2.Object]
             await self.finalize()
         else:
             await self.flush()
-            await self.write_obj_stream.close()
+
+        await self.write_obj_stream.close()
 
         self._is_stream_open = False
         self.offset = None

tests/unit/asyncio/test_async_appendable_object_writer.py

@@ -313,7 +313,7 @@ async def test_finalize_on_close(mock_write_object_stream, mock_client):
     result = await writer.close(finalize_on_close=True)
 
     # Assert
-    mock_stream.close.assert_not_awaited()  # Based on new implementation
+    mock_stream.close.assert_awaited_once()
     assert not writer._is_stream_open
     assert writer.offset is None
     assert writer.object_resource == mock_resource