AP_Compass: flag compass cal as long expected delay

libraries/AP_Compass/CompassCalibrator.cpp

@@ -780,6 +780,9 @@ bool CompassCalibrator::calculate_orientation(void)
         return true;
     }
 
+    // this function is very slow
+    hal.scheduler->expect_delay_ms(1000);
+
     float variance[ROTATION_MAX] {};
 
     for (enum Rotation r = ROTATION_NONE; r<ROTATION_MAX; r = (enum Rotation)(r+1)) {
@@ -846,6 +849,8 @@ bool CompassCalibrator::calculate_orientation(void)
         gcs().send_text(MAV_SEVERITY_INFO, "Mag(%u) new orientation: %u was %u %.1f", _compass_idx, besti, _orientation, (double)_orientation_confidence);
     }
 
+    hal.scheduler->expect_delay_ms(0);
+    
     if (!pass) {
         set_status(COMPASS_CAL_BAD_ORIENTATION);
         return false;