autotest: add trivial test just to cover the Airspeed_DLVR code

Tools/autotest/ArduPlane_Tests/AirspeedDrivers/ap1.txt

@@ -0,0 +1,9 @@
+QGC WPL 110
+0	1	0	16	0	0	0	0	-35.362881	149.165222	582.000000	1
+1	0	3	22	0.000000	0.000000	0.000000	0.000000	-35.361553	149.163956	100.000000	1
+2	0	3	16	0.000000	0.000000	0.000000	0.000000	-35.364540	149.162857	100.000000	1
+3	0	3	16	0.000000	0.000000	0.000000	0.000000	-35.361721	149.161835	40.000000	1
+4	0	3	178	0.000000	13.00000	0.000000	0.000000	0.000000	0.000000	0.000000	1
+5	0	3	16	0.000000	0.000000	0.000000	0.000000	-35.367970	149.164124	28.000000	1
+6	0	3	16	0.000000	0.000000	0.000000	0.000000	-35.366814	149.165878	28.000000	1
+7	0	3	21	0.000000	0.000000	0.000000	0.000000	-35.362911	149.165222	0.000000	1

Tools/autotest/arduplane.py

@@ -1853,6 +1853,13 @@ class AutoTestPlane(AutoTest):
 
         self.progress("Mission OK")
 
+    def test_airspeed_drivers(self):
+        self.set_parameter("ARSPD2_TYPE", 7)
+        self.reboot_sitl()
+        self.wait_ready_to_arm()
+        self.arm_vehicle()
+        self.fly_mission("ap1.txt")
+
     def fly_terrain_mission(self):
 
         self.customise_SITL_commandline([], wipe=True)
@@ -2157,6 +2164,10 @@ class AutoTestPlane(AutoTest):
              "Test EKF3 Affinity and Lane Switching",
              self.ekf_lane_switch),
 
+            ("AirspeedDrivers",
+             "Test AirSpeed drivers",
+             self.test_airspeed_drivers),
+
             ("LogUpload",
              "Log upload",
              self.log_upload),