I joined this mailing list after I googled and found this thread.

https://www.redhat.com/archives/libvir-list/2015-June/msg00583.html

Part of this thread read:

>So, further digging led me to [2], which in essence was the section of the libvirtd wiki page that the page claimed >was obsolete. Creating the .pkla authorization file finally enabled non-root privileged user management of a remote > >KVM host.

I was having this same problem, and I believe that what was needed was just the last usermod that added the non-root user to the libvirt group. I did just that one line and things seemed to be much happier.