add_backend() sometimes requires an additional argument

[umlaeute]

varnish's random() and hash() directors, require an additional argument in the add_backend() function (a weight, how often the added backend will be chosen).

however, the buildout generates something like:

sub vcl_init {
    # configure directors for load balancing
    new balancer_0 = directors.random();
    balancer_0.add_backend(backend_000);
}

which will be invalid if the chosen balancer is hash() or random() (as in the example), in which case we would need:

sub vcl_init {
    # configure directors for load balancing
    new balancer_0 = directors.random();
    balancer_0.add_backend(backend_000, 1.0);
}