chore: Modify test environment detection

[Slider0007]

Avoid accidentally using test environment config if any forwarding to loopback address 127.0.0.1 is configured (jomjol#2681)

/* The WebUI can also be executed on a local webserver for development purposes, e.g. XAMPP.
* Configure the physical device IP which shall be used for communication and call http://localhost
* NOTE: And you also might have to disable CORS in your webbrowser.
* IMPORTANT: For regular WebUI operation this IP parameter is not needed at all!
*/
var DUTDeviceIP = "192.168.2.68";      // Set the IP of physical device under test

(Inspired by jomjol@36c12b4)