Description of problem：
RHEL6 guest can't boot into OS on MTV because the virtio disk of rhel6 guest needs model='virtio-transitional'

Version-Release number of selected component (if applicable):
 MTV 2.7.8 with iib:894919 and OCP4.16.10
 
How reproducible:
100%

Steps:
1. Migrate a rhel6 guest from VMware on MTV
2. Check the guest after migration, but the guest can't boot into OS because the virtio disk of rhel6 guest needs model='virtio-transitional', please refer to screenshot 'rhel6-guest-on-MTV.png'

Actual Result:
As above description

Excepted Result:
Fix the bug

Additional info:
Can't reproduce the bug on rhel9.6 because the disk of the rhel6 guest has model='virtio-transitional', which was fixed by https://bugzilla.redhat.com/show_bug.cgi?id=1942325