Fix active discovery command

[leotaglia]

Description

This fixes the active_discovery_command error "Active discovery failed: can't convert nil into Integer" when trying to use the property on the kitchen.yml

Check List

• [ ] New functionality includes tests
• [ ] All tests pass
• [ ] All commits have been signed-off for the Developer Certificate of Origin. See https://github.com/chef/chef/blob/master/CONTRIBUTING.md#developer-certification-of-origin-dco
• [ ] PR title is a worthy inclusion in the CHANGELOG

Author: Leonardo Tagliabue leotaglia@gmail.com

Fix return value on function.

Obvious fix.