void waitForReplies() throws InterruptedException {
            synchronized (this) {
                while (waitingFor > 0) {
                    this.wait();
                }
            }
        }
This is used for testing and benchmarking rpc docsum interface.
time vespa-summary-benchmark file-containing-docids connectionspec summary-class repetitions threads
fx ' time vespa-summary-benchmark feed.xml tcp/localhost:19115 keyvaluesummary 10000 32'

@author baldersheim
vespaclient-java/src/main/java/com/yahoo/vespasummarybenchmark/VespaSummaryBenchmark.java