private static URI createMetricsProxyURI(String hostname) {
        return URI.create("http://" + hostname + ":19092/metrics/v1/values?consumer=Vespa");
    }
Finds all hosts we want to fetch metrics for, generates the appropriate URIs
and returns the generated MetricsResponse.

@author olaa
configserver/src/main/java/com/yahoo/vespa/config/server/metrics/DeploymentMetricsRetriever.java