Logstash permissions issue on fresh install

I might be mistaken, but it appears that the deb installer assigns the wrong permissions to Logstash's data directories during installation.

Queue and dead_letter_queue are both owned by root and in the root group after installation, but the logstash service runs as logstash and can't write to those directories. Changing ownership of the directories solves it (either `chown logstash ...` or `chgrp logstash ... ` followed by `chmod 775 ...`

**To reproduce:**

Unless I followed the instructions wrong, I just followed along the guides on your website for installing ELK stack 5.5 on Ubuntu. Using Ubuntu Server 16.0.4 LTS. The service would start but be non-functional until the ownership was changed.

Again I could have done something wrong on my end.