private ScanResponse scan(HBaseRpcController hrc, ScanRequest req) throws IOException {
    BlockingRpcCallback<ScanResponse> callback = new BlockingRpcCallback<>();
    STUB.scan(hrc, req, callback);
    return callback.get();
  }
Testcase to make sure that we do not close scanners if ScanRequest.numberOfRows is zero. See
HBASE-18042 for more details.
hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestScanWithoutFetchingData.java