Changing the bufferFactor so the correct address gets written to

When writing to address 5, you need to write to buffer 10. Not 40. address 2 * 8 bufferFactor = writing to address 4. what is not correct <!-- Thank you for contributing to this project! Please make sure you've read our contributing guidelines (https://github.com/BiancoRoyal/node-red-contrib-modbus/blob/develop/.github/CONTRIBUTING.md) --> **Which issues are addressed by this Pull Request?** Incorrect writing addresses in the modbus Server **What does this Pull Request change?** Set buffer factor to 2, from 8. **Does this Pull Request introduce any potentially breaking changes?** <!-- If you have made any changes to the message format sent between units or to a node's configuration, please include bullet points of what changed and what a current user needs to update to keep the same behavior they have with the previous version. -->