kill the now useless 'cleanup' parameter of routing_get_route_and_latency

kill the now useless 'cleanup' parameter of routing_get_route_and_latency

Instead, if route == NULL we won't bother collecting the route, so
freeing is useless.
If *route == NULL, we create a short-lived dynar (equivalent to the
result of having cleanup=1 previously
else, we fill that route without messing with it