CDC: Disable flusher 'initial snapshot optimisation'

    // A disk snapshot has unique items and if we're receiving a vbucket from

    // the start (seqno 0), we can issue Insert operations. This benefits some

    // KVStore implementations since a lookup isn't needed. This scenario

    // commonly occurs in rebalance where a vbucket is taken over by a new node.

    if (toFlush.ranges.size() == 1 &&

        toFlush.checkpointType == CheckpointType::InitialDisk) {

        writeOp = WriteOperation::Insert;

    }