The LocalSet accept loop blocked on ws_rx.recv() forever because the
detached accept thread kept a ws_tx clone alive, so the channel never
closed and start_with_full_serve_options never returned. cdp_processor
caught Ctrl-C and saved cookies, but that only ended its own task.
Add a shared shutdown flag and Notify. On Ctrl-C cdp_processor sets the
flag and notifies; the accept loop selects on the notify and breaks, so
run_until returns and the process exits. The accept thread checks the
flag between connections so it stops and drops ws_tx on the slow path.
Closes#225
SGavrl
1b9be08767