Use EV3 ultrasonic single-shot measurement algorithm from EV3 Lab software

lib/ev3/sonic.py

@@ -25,12 +25,14 @@ class UltrasonicSensor(EV3UartSensor):
     def distance(self, silent=False) -> int:
         """
         Measure the distance to the nearest obstacle in front of the sensor.
+        :param silent: If true, the ultrasonic sensor will not emit more
+                       sound waves after the measurement finishes.
         :return: Distance in millimeters or a magic value of 2550 if the measurement fails.
         """
-        cont_value = self.read_raw_mode(UltrasonicSensor.MODE_CONTINUOUS_CM)[0]
+        value = self.read_raw_mode(UltrasonicSensor.MODE_CONTINUOUS_CM)[0]
         if silent:
-            self.start_set_mode(UltrasonicSensor.MODE_SINGLE_CM)
-        return cont_value
+            value = self.read_raw_mode(UltrasonicSensor.MODE_SINGLE_CM)[0]
+        return value
 
     def presence(self) -> bool:
         """