@Override
  public boolean isSendComplete() {
    return sizeInBytes() == sentBytes;
  }
Override the release method from {@link RequestOrResponse}. When the {@link #prepareBuffer()} is not invoked, there
will be {@link #toSend}'s content waiting for releasing.
@return
ambry-protocol/src/main/java/com/github/ambry/protocol/GetResponse.java