Description of problem:
To create VMExport object we need to specify the APIGroup of exported object

Version-Release number of selected component (if applicable):
4.12

How reproducible:
Always

Steps to Reproduce:
1. Create a VM
2. Create a VMSnapshot
3. Create a VMExport for VMSnapshot without specifying the APIGroup

$ cat vmexport-snapshot.yaml
apiVersion: export.kubevirt.io/v1alpha1
kind: VirtualMachineExport
metadata:
name: export-vmsnapshot
spec:
source:
kind: VirtualMachineSnapshot
name: my-vmsnapshot
tokenSecretRef: virt-export-token

Actual results:
The VMExport was created, but it is not Ready and doesn't show any error

$ oc get virtualmachineexport
NAME SOURCEKIND SOURCENAME PHASE
export-vmsnapshot VirtualMachineSnapshot my-vmsnapshot

Expected results:
VMExport will fail to create saying APIGroup needs to be specified