Reset state before Step 8 in SWTCH 2.6 test (project-chip#38262)

Switch test 2.6 Step 6 is doing more switch actions then configured leading into the "cancelled" state which means that no more event should be send

(from spec 1.13.5.3. MultiPressMax Attribute)
> until the switch has become
fully idle (i.e. no longer in the process of counting presses within the multipress).

The test is starting step 8 directly after receiving the MultiPressComplete event from step 6 and not giving the Switch the time to finish multi switch actions.

This PR adds a reset after Step 6 before Step 8 to ensure this is cleared

Author: Apollon77

src/python_testing/TC_SWTCH.py

@@ -924,6 +924,8 @@ def test_multi_press_sequence(starting_step: str, count: int, short_long: bool =
         # subscription is already established
         self.step("7b")
 
+        self._ask_for_switch_idle(endpoint_id)
+
         test_multi_press_sequence("8a", count=2, short_long=True)
 
         self.step("9a")