private HostSpec findHost(String hostName, Set<HostSpec> hosts) {
            for (HostSpec host : hosts)
                if (host.hostname().equals(hostName))
                    return host;
            return null;
        }
Returns a host by cluster name and index, or null if there is no host with the given values in this
node-repository/src/test/java/com/yahoo/vespa/hosted/provision/provisioning/ProvisioningTest.java