* Close entity->pdusession_sock manually before pthread_join() to unblock sdap_tun_read_thread()
* Update tun_destroy() to open a fresh socket for interface management, independent from the data socket
* Fix check on success of change_interface_state() in tun_destroy(): is a boolean
* Handle ENODEV error when bringing interface down: treat as success if the interface is already gone.
* tun_destroy() is now handling INTERFACE_DOWN, so `INTERFACE_DOWN` in `tun_config()` is no longer needed