void setOnPollLatch(CountDownLatch onPollLatch) {
    this.onPollLatch = onPollLatch;
  }
Sets {@link CountDownLatch} to be counted down on {@link #onPollReady()}
@param onPollLatch {@link CountDownLatch} that needs to be set
ambry-router/src/test/java/com/github/ambry/router/GetBlobInfoOperationTest.java