AP_InertialSensor: fix accelcalsimple watchdog

libraries/AP_InertialSensor/AP_InertialSensor.cpp

@@ -1860,6 +1860,7 @@ MAV_RESULT AP_InertialSensor::simple_accel_cal()
         return MAV_RESULT_TEMPORARILY_REJECTED;
     }
 
+    hal.scheduler->expect_delay_ms(20000);
     // record we are calibrating
     _calibrating = true;
 
@@ -1999,6 +2000,8 @@ MAV_RESULT AP_InertialSensor::simple_accel_cal()
     // stop flashing leds
     AP_Notify::flags.initialising = false;
 
+    hal.scheduler->expect_delay_ms(0);
+
     return result;
 }