tests: pull images from cloud.centos.org

temporary work around vagrant cloud issue which seems broken at the time
of pushing this commit.
Let's pull images from cloud.centos.org for now since vagrant cloud
hosted images return a 403 error.

Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>

tests/scripts/vagrant_up.sh

@@ -1,5 +1,8 @@
 #!/bin/bash
 
+vagrant box remove --force --provider libvirt --box-version 0 centos/8 || true
+vagrant box add --provider libvirt --name centos/8 https://cloud.centos.org/centos/8/vagrant/x86_64/images/CentOS-8-Vagrant-8.3.2011-20201204.2.x86_64.vagrant-libvirt.box || true
+
 retries=0
 until [ $retries -ge 5 ]
 do