fix(testing): Move CloseSession call after factory reset in TC_CGEN_2_8

The current implementation of commissioner.CloseSession only marks the session
as defunct rather than fully closing it. This state can be reactivated if
messages are exchanged on the session.

By moving the CloseSession call to after the factory reset step, we ensure
that the device session is already destroyed before marking it as defunct,
preventing any possibility of message exchange that could reactivate the
session. This allows the commissioner to successfully create a new session
in subsequent steps.

A follow-up change will be needed to properly fix the CloseSession function
to use MarkForEviction instead of MarkAsDefunct, and potentially rename the
current function to better reflect its behavior.

Author: swan-amazon

src/python_testing/TC_CGEN_2_8.py

@@ -129,15 +129,15 @@ async def test_TC_CGEN_2_8(self):
             "First CommissioningComplete failed",
         )
 
-        # Close the commissioner session with the device to clean up resources
-        commissioner.CloseSession(nodeid=self.dut_node_id)
-
         # Step 5: Factory reset is handled by test operator
         self.step(5)
         if not self.check_pics('PICS_USER_PROMPT'):
             self.skip_all_remaining_steps(6)
             return
 
+        # Close the commissioner session with the device to clean up resources
+        commissioner.CloseSession(nodeid=self.dut_node_id)
+
         self.wait_for_user_input(prompt_msg="Manually trigger factory reset on the DUT, then continue")
 
         # Step 6: Put device in commissioning mode (requiring user input, so skip in CI)