blacklistIPs JS configuration isn't parsed correctly, pt. 2

[imiric]

We recently noticed an error parsing the blacklistIPs option in the Cloud, see https://loadimpact.slack.com/archives/CM53T6UFJ/p1625472145025000.

The error is:

json: cannot unmarshal object into Go struct field Options.options.blacklistIPs of type *lib.IPNet

This is similar to #973, but it seems #1004 didn't fully address the issue and we might also need a MarshalText() implementation.

Environment

• k6 version: v0.33.0
• OS and version: k6 Cloud
• Docker version and image, if applicable: N/A

Expected Behavior

The option shouldn't cause an Aborted by script error and should work in the Cloud as well.

Actual Behavior

The test run is Aborted by script.

Steps to Reproduce the Problem

Run a script like the following in the Cloud (via the web UI):

import { sleep } from 'k6';

export const options = {
  blacklistIPs: ['10.0.0.0/8'],
  vus: 1,
  duration: '30s',
}

export default function () {
  sleep(30);
}