[lib.sh] Support older jumpserver libvirt

`virsh undefine` argument `--nvram` is only supported by newer
versions of libvirt.
Although this is mandatory for AArch64, for x86_64 this is not a
blocker (since we don't enable OVMF for the VMs on the jumpserver).

Change-Id: I3a82bc54b36228980a41d77a463a7558a685c03d
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>