TROVE-2017-004: Fix assertion failure in relay_send_end_cell_from_edge_

This fixes an assertion failure in relay_send_end_cell_from_edge_() when an
origin circuit and a cpath_layer = NULL were passed.

A service rendezvous circuit could do such a thing when a malformed BEGIN cell
is received but shouldn't in the first place because the service needs to send
an END cell on the circuit for which it can not do without a cpath_layer.

Fixes #22493

Reported-by: Roger Dingledine <arma@torproject.org>
Signed-off-by: David Goulet <dgoulet@torproject.org>
connection_edge_reached_eof(edge_connection_t *conn)
{
  if (connection_get_inbuf_len(TO_CONN(conn)) &&
      connection_state_is_open(TO_CONN(conn))) {
    /* it still has stuff to process. don't let it die yet. */
    return 0;
  }
  log_info(LD_EDGE,"conn (fd "TOR_SOCKET_T_FORMAT") reached eof. Closing.",
           conn->base_.s);
  if (!conn->base_.marked_for_close) {
    /* only mark it if not already marked. it's possible to
     * get the 'end' right around when the client hangs up on us. */
    connection_edge_end(conn, END_STREAM_REASON_DONE);
    if (conn->base_.type == CONN_TYPE_AP) {
      /* eof, so don't send a socks reply back */
      if (EDGE_TO_ENTRY_CONN(conn)->socks_request)
        EDGE_TO_ENTRY_CONN(conn)->socks_request->has_finished = 1;
    }
    connection_mark_for_close(TO_CONN(conn));
  }
  return 0;
}

connection_edge_reached_eof(edge_connection_t *conn)
{
  if (connection_get_inbuf_len(TO_CONN(conn)) &&
      connection_state_is_open(TO_CONN(conn))) {
    /* it still has stuff to process. don't let it die yet. */
    return 0;
  }
  log_info(LD_EDGE,"conn (fd "TOR_SOCKET_T_FORMAT") reached eof. Closing.",
           conn->base_.s);
  if (!conn->base_.marked_for_close) {
    /* only mark it if not already marked. it's possible to
     * get the 'end' right around when the client hangs up on us. */
    connection_edge_end(conn, END_STREAM_REASON_DONE);
    if (conn->base_.type == CONN_TYPE_AP) {
      /* eof, so don't send a socks reply back */
      if (EDGE_TO_ENTRY_CONN(conn)->socks_request)
        EDGE_TO_ENTRY_CONN(conn)->socks_request->has_finished = 1;
    }
    connection_mark_for_close(TO_CONN(conn));
  }
  return 0;
}
