private boolean isFree(int port) {
        return portFinder.isFree(port) && !portDB.containsKey(port);
    }
Returns the baseport of the first available port range of length numPorts,
or 0 if there is no range of that length available.
TODO: remove this API

@param numPorts the length of the desired port range.
@return the baseport of the first available range, or 0 if no range is available.
config-model/src/main/java/com/yahoo/vespa/model/HostPorts.java