LPS-50452 Migrate Portal Settings portlet aui-base javascript

In this case, form.fm('defaultLdap') returns a `RadioNodeList` (https://developer.mozilla.org/en-US/docs/Web/API/RadioNodeList), the `value` property will be the value of the checked radio.

For whatever reason trying to access the value with `.val()` will throw an error with a `RadioNodeList`

Not sure where the source of that issue is.