autotest: let heading settle before testing WP_YAW_BEHAVIOR=0

2022-08-19T02:22:48.3161982Z AT-0229.9: Exception caught: Unexpected heading=94.000000 want=91.000000
2022-08-19T02:22:48.3162341Z Traceback (most recent call last):
2022-08-19T02:22:48.3162738Z   File "/__w/ardupilot/ardupilot/Tools/autotest/common.py", line 7173, in run_one_test_attempt
2022-08-19T02:22:48.3163101Z     test_function()
2022-08-19T02:22:48.3163507Z   File "/__w/ardupilot/ardupilot/Tools/autotest/arducopter.py", line 4414, in GuidedSubModeChange
2022-08-19T02:22:48.3164012Z     self.assert_heading(orig_heading)
2022-08-19T02:22:48.3164419Z   File "/__w/ardupilot/ardupilot/Tools/autotest/common.py", line 5610, in assert_heading
2022-08-19T02:22:48.3164866Z     raise NotAchievedException("Unexpected heading=%f want=%f" %
2022-08-19T02:22:48.3165290Z common.NotAchievedException: Unexpected heading=94.000000 want=91.000000

Tools/autotest/arducopter.py

@@ -4407,8 +4407,9 @@ class AutoTestCopter(AutoTest):
         self.fly_guided_move_local(5, 5, 10)
 
         self.start_subtest("Checking that WP_YAW_BEHAVIOUR 0 works")
-        orig_heading = self.get_heading()
         self.set_parameter('WP_YAW_BEHAVIOR', 0)
+        self.delay_sim_time(2)
+        orig_heading = self.get_heading()
         self.fly_guided_move_local(5, 0, 10)
         # ensure our heading hasn't changed:
         self.assert_heading(orig_heading)