You don't need to specify the full path here. webinos-api-iot is located inside a node_modules folder among with the drivers. Due to require's way of loading modules, using the driverHandleModuleName along, should work fine. You can replace this line with:
var driverHandle = require(driverHandleModuleName);

Alternatively, you can use the global variable  moduleLocation like this:
var driverHandle = require(path.join(moduleLocation, driverHandleModuleName));