public CompletableFuture<Boolean> start(HBaseRpcController controller,
      ScanResponse respWhenOpen) {
      return build().start(controller, respWhenOpen);
    }
Short cut for {@code build().start(HBaseRpcController, ScanResponse)}.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncRpcRetryingCallerFactory.java