Tools: autotest: remove needless wrappers, initialisation etc around guided-submode test

Also disable disarm delay due to autotest mavlink traffic issues

Tools/autotest/arducopter.py

@@ -2318,16 +2318,12 @@ class AutoTestCopter(AutoTest):
     def fly_guided_change_submode(self):
         """"Ensure we can move around in guided after a takeoff command."""
 
-        self.context_push()
-
-        ex = None
-        try:
         '''start by disabling GCS failsafe, otherwise we immediately disarm
         due to (apparently) not receiving traffic from the GCS for
         too long.  This is probably a function of --speedup'''
         self.set_parameter("FS_GCS_ENABLE", 0)
-            self.mavproxy.send('mode guided\n')  # stabilize mode
-            self.wait_mode('GUIDED')
+        self.set_parameter("DISARM_DELAY", 0) # until traffic problems are fixed
+        self.change_mode("GUIDED")
         self.wait_ready_to_arm()
         self.arm_vehicle()
 
@@ -2344,21 +2340,7 @@ class AutoTestCopter(AutoTest):
         self.fly_guided_stop()
         self.fly_guided_move_local(5, 5, 10)
 
-            self.progress("Landing")
-            self.mavproxy.send('switch 2\n')  # land mode
-            self.wait_mode('LAND')
-            self.mav.motors_disarmed_wait()
-
-        except Exception as e:
-            self.progress("Exception caught")
-            ex = e
-
-        self.context_pop()
-        self.zero_throttle()
-        self.reboot_sitl()
-
-        if ex is not None:
-            raise ex
+        self.do_RTL()
 
     def test_gripper_mission(self):
         self.context_push()