Set vm_info to kvm for Hetzner virtual machines

[Teluka]

[Impact]

Hetzner virtual machine type is not a recognized VM type in Landscape and thus won't allow use of a Virtual Guest asset to register with.

The Hetzner type uses a KVM-family hypervisor (displaying "Hetzner" in sys_vendor which landscape-client doesn't recognize, thus cannot associate/map to kvm)

[Test Case]

 * Deploy a Hetzner virtual machine
 * Look sys_vendor
   $ cat /sys/class/dmi/id/sys_vendor
   Hetzner

 * Install landscape-client
 * Register the client to the desired landscape-server
 * Verify "VM Type" to be "kvm" under the computer info (in landscape-server)

What's interesting is that chassis_vendor is reporting that QEMU is used therefore landscape-client could use/check that field as well when discovering VM types.

> cat sys/class/dmi/id/chassis_vendor
QEMU

[Other Info]

 * Upstream pull request:
   https://github.com/CanonicalLtd/landscape-client/pull/52

[Simon Poirier (simpoir)]

I tried to reproduce on a hetzner cloud 18.04 instance and landscape-client detected virt as expected.