Fix to "Running with Init" script

Logstash team,

I first wanted to say thank you for your work on this project. I've recently set it up at work (along with Kibana), and have amazed quite a few colleagues with just what I've been able to do with them.

When I was working on getting Logstash stood up, I referred to the "Running with Init" example in the Logstash cookbook to (obviously) create an init script.  I got it to work eventually, but it failed out of the box (on two different versions of CentOS, for reference).  I believe I found the cause of the failure, and included my one line change in this pull request.

Thank you again,
- Christian