Permanent write failures can happen if pipeline recoveries occur for the first packet

We have observed that write fails permanently if the first packet doesn't go through properly and pipeline recovery happens. If the write op creates a pipeline, but the actual data packet does not reach one or more datanodes in time, the pipeline recovery will be done against the 0-byte partial block.

If additional datanodes are added, the block is transferred to the new nodes. After the transfer, each node will have a meta file containing the header and 0-length data block file. The pipeline recovery seems to work correctly up to this point, but write fails when actual data packet is resent.