@Override
    public void set(String key, Number val, Metric.Context ctx) {
        ForwardingContext fwd = (ForwardingContext)ctx;
        for (int i = 0; i < consumers.length; ++i) {
            consumers[i].set(key, val, fwd != null ? fwd.contexts[i] : null);
        }
    }
If more than one {@link MetricConsumerFactory} is registered in a container, calls to <code>Metric</code> need to be
forwarded to all the underlying <code>MetricConsumers</code>. That is the responsibility of this class.
Instances of this class is created by the {@link MetricConsumerProvider} in those cases.

@author Simon Thoresen Hult
container-disc/src/main/java/com/yahoo/container/jdisc/metric/ForwardingMetricConsumer.java