Fix gluster peered state

It's just a bug fix and some comments that I thought were helpful (but which might not conform too closely with the established style, not sure).  

The bug just fixed a case where using the state.glusterfs.peered would return "none" and this would throw an error. Now it won't throw an error. I'm pretty sure it would do this when you ran "salt '*' state.hightstate test=true".

My first github pull request, but I'm doing my best to follow the guidelines from: http://docs.saltstack.com/en/latest/topics/development/contributing.html