Fix LEController peripheral mode on BlueZ

LEController in peripheral mode uses QBluetoothSocket::setSocketDescriptor().
Since QBluetoothsocket was ported to DBus (enabled when Bluez is 5.46 or later)
setSocketDescriptor()/server mode does not work. That's why
f602d7fe

 made sure that QBluetoothServer
uses the old raw socket implementation. Unfortunately QLowEnergyController
was forgotten and needs the same workaround.

Change-Id: I6ba3654ee199d0ffcf4b69f16dfbc5508d6b13d4
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>