public PrimeConnectionEndStats getEndStats() {
        return stats;
    }
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