`dragonfly/tiering_test.py::test_full_sync[df_factory0] ` failing during shutdown

https://github.com/dragonflydb/dragonfly/actions/runs/20089095519/job/57632683127

does not seem related to closed issue https://github.com/dragonflydb/dragonfly/issues/5484

might not be related to test code, fails during teardown

```
dragonfly/instance.py:263: in stop
self.sed_proc.communicate()

...
E ValueError: I/O operation on closed file.

/usr/lib/python3.8/subprocess.py:1015: ValueError
```

Start with the failing dragonfly/tiering_test.py::test_full_sync[df_factory0] run and the teardown traceback in dragonfly/instance.py:263, where stop() calls sed_proc.communicate(). Reproduce the shutdown failure from the linked Actions run, determine why the subprocess stream is already closed, and confirm the test completes without the ValueError.

Written by the indexing model from the issue text.