ZBD distributed TC mode only when TC address is NOT provided

[geoffrey-vl]

Currently when the TC address is provided in the ZigbeeDirect OOB joining method, the code sets Distributed TC mode and also reports the TC address as FF:FF: instead of the TC address that was passed over BLE.

However, according to the Zigbee Direct specs:

In case the Trust Center TLV is omitted, then the device will set the trust center address to
0xFFFFFFFFFFFFFFFF (for distributed security).

So it's the other way around that what is in the code.
After applying this patch, and passing a TC address during the OOB joining, I now see the TC address also in the commissioning status.