Libvirt test provider for virt-test

This is the official test provider [1] for the following subtest types:

Libvirt
LVSB
V2V
Libguestfs

Really quick start guide

Fork this repo on github
Create a new topic branch for your work
Create a new test provider file in your virt test repo, like:
```
cp io-github-autotest-libvirt.ini myprovider.ini
```
```
[provider]
uri: file:///home/foo/Code/tp-libvirt
[libvirt]
subdir: libvirt/
[libguestfs]
subdir: libguestfs/
[lvsb]
subdir: lvsb/
[v2v]
subdir: v2v/
```
You can optionally delete temporarily the io-github-autotest-qemu.ini file, just so you don't have test conflicts. Then you can develop your new test code, run it using virt test, and commit your changes.
Make sure you have inspektor installed.

Run:

inspekt checkall --disable-style E501,E265,W601,E402,E722,E741 --no-license-check <test_script_name>.py

Ensure <https://github.com/autotest/tp-libvirt/blob/master/tp-libvirt_review_comment_summary.rst> are met
Fix any problems
Push your changes and submit a pull request
That's it.

[1]	You can always create your own test provider, if you have special purposes, or just want to develop your work independently.