@Override
            public void primeCompleted(Server s, Throwable lastException) {
                if (lastException == null) {
                    successCount.incrementAndGet();
                    s.setReadyToServe(true);
                } else {
                    failureCount.incrementAndGet();
                }
                latch.countDown();
            }
Prime connections, blocking until configured percentage (default is 100%) of target servers are primed 
or max time is reached.

@see CommonClientConfigKey#MinPrimeConnectionsRatio
@see CommonClientConfigKey#MaxTotalTimeToPrimeConnections
ribbon-loadbalancer/src/main/java/com/netflix/client/PrimeConnections.java