handle_establish_intro() can mark circuits for close twice

Some of the failure cases in handle_verified_establish_intro_cell() mark the circuit for close. So if handle_establish_intro() tries to mark it for close again, it will trigger a bug warning.

I think this is the only case in the v3 introduce protocol. We should check for cases like this in the v3 rend protocol as well.

  /* This cell is legit. Take the appropriate actions. */
  cell_ok = handle_verified_establish_intro_cell(circ, parsed_cell);
  if (cell_ok < 0) {
    goto err;
  }

  log_warn(LD_GENERAL, "Established prop224 intro point on circuit %" PRIu32,
           circ->p_circ_id);

  /* We are done! */
  retval = 0;
  goto done;

 err:
  circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_TORPROTOCOL);