private int getCorePoolSize() {
            int propSize = poolSizeProp.get();
            if (propSize > 0) {
                return propSize;
            }
            return 2; // default
        }
A server list updater for the {@link com.netflix.loadbalancer.DynamicServerListLoadBalancer} that
utilizes eureka's event listener to trigger LB cache updates.

Note that when a cache refreshed notification is received, the actual update on the serverList is
done on a separate scheduler as the notification is delivered on an eurekaClient thread.

@author David Liu
ribbon-eureka/src/main/java/com/netflix/niws/loadbalancer/EurekaNotificationServerListUpdater.java