Plane: call update_loiter before determining whether to fly home or not

we are calling "reached_loiter_target" as part of our checks as to whether to fly home or not.

We need to call update_loiter so the L1 controller can update its internal state for the new waypoint which do_RTL has set.  Depending on location (but typically), that will mean that L1's reached_loiter_target() will then return false, so we fly home.

This bug was affected by f8d7be5 .  Any sort of altitude error greater than 10m would delay us entering the landing sequence, allowing the L1 controller to update its state.

ArduPlane/mode_rtl.cpp

@@ -95,6 +95,13 @@ void ModeRTL::navigate()
     }
 #endif
 
+    uint16_t radius = abs(plane.g.rtl_radius);
+    if (radius > 0) {
+        plane.loiter.direction = (plane.g.rtl_radius < 0) ? -1 : 1;
+    }
+
+    plane.update_loiter(radius);
+
     if (!plane.auto_state.checked_for_autoland) {
         if ((plane.g.rtl_autoland == RtlAutoland::RTL_IMMEDIATE_DO_LAND_START) ||
             (plane.g.rtl_autoland == RtlAutoland::RTL_THEN_DO_LAND_START &&
@@ -116,13 +123,6 @@ void ModeRTL::navigate()
                 plane.auto_state.checked_for_autoland = true;
             }
     }
-
-    uint16_t radius = abs(plane.g.rtl_radius);
-    if (radius > 0) {
-        plane.loiter.direction = (plane.g.rtl_radius < 0) ? -1 : 1;
-    }
-
-    plane.update_loiter(radius);
 }
 
 #if HAL_QUADPLANE_ENABLED