Method foreachvalue

src/http.cpp:2174–2176

NOTE: we know that no more sockets will be accepted because the accept loop is on `self()` and we're in `finalize()`.

    // NOTE: we know that no more sockets will be accepted because
    // the accept loop is on `self()` and we're in `finalize()`.
    foreachvalue (Client& client, clients) {
      client.serving.discard();
    }

    clients.clear();
  }