[Enhancement] Avoid race conditions when multiple Gunthy GUI instances write to same file

[caogeoge]

Hi Sjakil,

With the implementation of multiple Gunthy GUI instances writing to the same gui-bots.json file, there might be race conditions between the different node.js processes trying to open, read & write to gui-bots.json. I don't know much about Node.js (and you probably have a better way) but with multiple Gunthy GUI instances you can avoid race condition when writing gui-bots.json in Node.js as following: https://stackoverflow.com/questions/28588707/node-js-check-if-a-file-is-open-before-copy