Plane: report bad AHRS health if uncalibrated accels with EKF

fixes issue #1720

ArduPlane/GCS_Mavlink.pde

@@ -224,6 +224,11 @@ static NOINLINE void send_extended_status1(mavlink_channel_t chan)
         // AHRS subsystem is unhealthy
         control_sensors_health &= ~MAV_SYS_STATUS_AHRS;
     }
+    if (ahrs.have_inertial_nav() && !ins.calibrated()) {
+        // trying to use EKF without properly calibrated accelerometers
+        control_sensors_health &= ~MAV_SYS_STATUS_AHRS;
+    }
+
     if (barometer.healthy()) {
         control_sensors_health |= MAV_SYS_STATUS_SENSOR_ABSOLUTE_PRESSURE;
     }