autotest: fix flapping fly-home-land-and-disarm

One of the tests just happened to be within acceptance radius of
waypoint 8 - so when we set that as a waypoint we never saw it actually
be our waypoint so the set_waypoint failed

Tools/autotest/arduplane.py

@@ -696,6 +696,10 @@ class AutoTestPlane(AutoTest):
         self.progress("Using %s to fly home" % filename)
         self.load_mission(filename)
         self.change_mode("AUTO")
+        # don't set current waypoint to 8 unless we're distant from it
+        # or we arrive instantly and never see it as our current
+        # waypoint:
+        self.wait_distance_to_waypoint(8, 100, 10000000)
         self.set_current_waypoint(8)
         self.drain_mav()
         # TODO: reflect on file to find this magic waypoint number?

Tools/autotest/common.py

@@ -4984,6 +4984,15 @@ class AutoTest(ABC):
             **kwargs
         )
 
+    def wait_distance_to_waypoint(self, wp_num, distance_min, distance_max, **kwargs):
+        # TODO: use mission_request_partial_list_send
+        wps = self.download_using_mission_protocol(mavutil.mavlink.MAV_MISSION_TYPE_MISSION)
+        m = wps[wp_num]
+        self.progress("m: %s" % str(m))
+        loc = mavutil.location(m.x / 1.0e7, m.y / 1.0e7, 0, 0)
+        self.progress("loc: %s" % str(loc))
+        self.wait_distance_to_location(loc, distance_min, distance_max, **kwargs)
+
     def wait_distance_to_location(self, location, distance_min, distance_max, timeout=30, **kwargs):
         """Wait for flight of a given distance."""
         assert distance_min <= distance_max, "Distance min should be less than distance max."