message: calibration: switch from serial to UDP
  This makes the test applicable for different platforms, and not just
  Linux.
diff: @@ -17,7 +17,7 @@ TEST(HardwareTest, GyroCalibration)
  {
  DroneCore dc;
  - ConnectionResult ret = dc.add_serial_connection("/dev/ttyACM0");
  + ConnectionResult ret = dc.add_udp_connection();
  ASSERT_EQ(ret, ConnectionResult::SUCCESS);
  // Wait for system to connect via heartbeat.
  @@ -41,7 +41,7 @@ TEST(HardwareTest, AccelerometerCalibration)
  {
  DroneCore dc;
  - ConnectionResult ret = dc.add_serial_connection("/dev/ttyACM0");
  + ConnectionResult ret = dc.add_udp_connection();
  ASSERT_EQ(ret, ConnectionResult::SUCCESS);
  // Wait for system to connect via heartbeat.
  @@ -65,7 +65,7 @@ TEST(HardwareTest, MagnetometerCalibration)
  {
  DroneCore dc;
  - ConnectionResult ret = dc.add_serial_connection("/dev/ttyACM0");
  + ConnectionResult ret = dc.add_udp_connection();
  ASSERT_EQ(ret, ConnectionResult::SUCCESS);
  // Wait for system to connect via heartbeat.
  