Fixes for vagrant/libvirt (#264)

## Description

Fixes some issues with running the vagrant setup using libvirt:
- Adds network name for libvirt private network
- Adds a host_ip for libvirt private network, to allow creation of the network if it doesn't already exist

## Why is this needed

Without these changes, vagrant-libvirt fails to provision the hosts or the private network.

## How Has This Been Tested?

Successfully ran through the local setup with vagrant instructions here: https://tinkerbell.org/docs/setup/local-with-vagrant/

Host OS: Fedora 32
Vagrant version: 2.2.9 (installed from RPM)
vagrant-libvirt version: 0.1.2 (installed using `vagrant plugin install`)

## How are existing users impacted? What migration steps/scripts do we need?

I don't expect any impact to existing users, unless those users were also running into issues standing up the vagrant stack with libvirt

## Checklist:

I have:

- [ ] updated the documentation and/or roadmap (if required)
- [ ] added unit or e2e tests
- [ ] provided instructions on how to upgrade

deploy/vagrant/Vagrantfile

@@ -16,6 +16,8 @@ Vagrant.configure('2') do |config|
 
     provisioner.vm.network :private_network,
                         virtualbox__intnet: "tink_network",
+                        libvirt__network_name: "tink_network",
+                        libvirt__host_ip: "192.168.1.254",
                         libvirt__dhcp_enabled: false,
                         libvirt__forward_mode: 'none',
                         auto_config: false
@@ -41,6 +43,7 @@ Vagrant.configure('2') do |config|
     worker.vm.network :private_network,
                       mac: "080027000001",
                       virtualbox__intnet: "tink_network",
+                      libvirt__network_name: "tink_network",
                       libvirt__dhcp_enabled: false,
                       libvirt__forward_mode: 'none',
                       auto_config: false