fix 'group libvirtd does not exist' bug

[AI-Memory]

It shows the bug as follows when I use setup_vagrant.sh to setup my host.

-----------------
Setting up libicu-dev (57.1-6ubuntu0.2) ...
Setting up libxml2-dev:amd64 (2.9.4+dfsg1-4ubuntu1.2) ...
Setting up libxslt1-dev:amd64 (1.1.29-2.1ubuntu1) ...
+ vagrant plugin install vagrant-libvirt
Installing the 'vagrant-libvirt' plugin. This can take a few minutes...
Installed the plugin 'vagrant-libvirt (0.0.40)'!
+ sudo adduser wg libvirtd
adduser: The group `libvirtd' does not exist.
-----------------

My host info:
Distributor ID: Ubuntu
Description: Ubuntu 17.10
Release: 17.10
Codename: artful
Linux wgwks 4.10.17-041017-generic #201705201051 SMP Sat May 20 14:53:33 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

[AdeshChoudhar]

@bigdata-memory
Try sudo adduser 'id-un' libvirt