bluez: fix build without bluez5-dun

    make[5]: Entering directory `./NetworkManager/_build/src/devices/bluetooth'
      CC       nm-bluez-device.lo
    ../../../../src/devices/bluetooth/nm-bluez-device.c: In function 'nm_bluez_device_disconnect':
    ../../../../src/devices/bluetooth/nm-bluez-device.c:430:5: error: "WITH_BLUEZ5_DUN" is not defined [-Werror=undef]
     #if WITH_BLUEZ5_DUN

Fixes: f1c9595311f52d8b79e8d2032e006005613a8fb1
Fixes: 751b52e50be049b53a0b998638a22d4e28a59135
Signed-off-by: Thomas Haller <thaller@redhat.com>
bluez: Another bluez5 build fix

Fixes the "unused declaration" warning with -Werror and no bluez-libs.

Fixes: f1c9595311f52d8b79e8d2032e006005613a8fb1
Fixes: 751b52e50be049b53a0b998638a22d4e28a59135