Test request order.

[horizonzy]

@merlimat Hi, Matteo. We found that there is a critical issue with the request order, when the request number is greater than the maxRequestsPerBatch, the put result will be out of order, could you help to check it?

[merlimat]

@horizonzy that is indeed a very good point. In general it was deemed to be ok to allow reordering of requests, though for sequenced keys we must be very precise. Let me think about a way to address this.