QBluetoothLocalDevice::isValid() returns wrong results

The QBluetoothLocalDevice on QNX and Bluez backend always returned true (no matter what).

First failure (on Bluez)

• Remove every Bluez device from the system
• Run following code:

  QBluetoothLocalDevice local;
  QVERIFY(!local.isValid())
  

  The above test fails on Bluez

Second failure (on QNX and Bluez)

• Ensure a Bluetooth device is connected
• Run following code:

  //assume that local device doesn't have the given address
  QBluetoothAddress a("FF:FF:FF:FF:FF:FF")  
  QBluetoothLocalDevice local(a);
  QVERIFY(!local.isValid())
  

  The above test fails on Bluez and QNX.