private static double toDouble(Duration duration) {
            return duration.toNanos()/1_000_000_000.0;
        }
Select the better of the two given GroupStatus objects, biased to the first
parameter. Thus, if all groups have equal coverage sufficiency, the one
currently at the needle will be used. Either parameter can be null, in which
case any non-null will be preferred.

@param first preferred GroupStatus
@param second potentially better GroupStatus
@return the better of the two
container-search/src/main/java/com/yahoo/search/dispatch/LoadBalancer.java