Destroy fails if virtual machine has checkpoints

[abbbi]

Latest libvirt versions have introduced checkpoints which are mostly used for backup purposes (https://libvirt.org/kbase/live_full_disk_backup.html)

In case a virtual machine deployed via vagrant-libvirt has such an existent checkpoint, destroy fails:

.vagrant.d/gems/3.1.4/gems/fog-libvirt-0.11.0/lib/fog/libvirt/requests/compute/vm_action.rb:7:in undefine': Call to virDomainUndefineFlags failed: Requested operation is not valid: cannot delete inactive domain with 3 checkpoints (Libvirt::Error)`

Possible solutions would be:

1. during vagrant destroy, remove existent checkpoints just as it is done with snapshots, one problem might be that
   removing checkpoints is only possible if virtual machine is running, or the checkpoint must be removed with metadata
   option only.

2. add flag during undefine that undefines the virtual machine and removes checkpoint metadata (like virsh handles with virsh undefine .. --checkpoints-metadata), if supported by the used libvirt version.

Workaround: remove checkpoints before issuing "vagrant destroy" using virsh.

The feature was "tech preview" as with libvirt version < 7006000 and can be considered beeing supported for any versions above.