Meta server: fix write behind (backward compatibility) replay log failure with chunk version roll back failure, by removing chunk version roll back entry in chunk allocation entry by using log chunk allocation write "RPC" if prior version of the chunk existed.
Meta server: fix write behind (backward compatibility) replay log failure with chunk version roll back failure, by removing chunk version roll back entry in chunk allocation entry by using log chunk allocation write "RPC" if prior version of the chunk existed.

quantcast/qfs,quantcast/qfs,quantcast/qfs,quantcast/qfs,quantcast/qfs,quantcast/qfs,quantcast/qfs,quantcast/qfs