Merge pull request #3550 from PX4/level_horizon

fix level horizon feature:

src/modules/commander/accelerometer_calibration.cpp

@@ -595,7 +595,8 @@ int do_level_calibration(int mavlink_fd) {
 	param_get(pitch_offset_handle, &pitch_offset_current);
 	param_get(board_rot_handle, &board_rot_current);
 
-	if (board_rot_current == 0) {
+	// give attitude some time to settle if there have been changes to the board rotation parameters
+	if (board_rot_current == 0 && fabsf(roll_offset_current) < FLT_EPSILON && fabsf(pitch_offset_current) < FLT_EPSILON ) {
 		settle_time = 0;
 	}