the OVF tests use `qemu-img`, which is provided by either our
pve-qemu(-kvm) or qemu-utils (upstream).
Use qemu-utils as it's provided by ours and upstreams package and
thus makes bootstrapping easier, e.g., if our qemu package is not yet
installed this can still be build.
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>