Description of problem:
In case we delete a VM while a migration is in progress and the VMIM isn't finished yet, the VMIM is cant be deleted, this also prevents the deletion of the namespace it was created


Version-Release number of selected component (if applicable):
4.11

How reproducible:
100%

Steps to Reproduce:
1. Create a number of VMs (15)
2. Start live migration on all of them
3. delete all the VMs
4. try to delete the VMIM

Actual results:
The VMIM still exists (VM + VMI are deleted)

Expected results:
The VMIM is deleted 

Additional info:
the VMIM finlizer section shows:
  finalizers:
  - kubevirt.io/migrationJobFinalize

the VMIM will be automatically deleted by editing the VMIM and removing the "finalizer" section

I think the best approach would be to delete the VMIM in case one exists before deleting the VMI.