Description of problem:

Try to migrate VM: "Home Assistant" from ova file: provided by rhn-support-mjankula 

https://github.com/home-assistant/operating-system/releases/download/15.2/haos_ova-15.2.ova

the plan hit error in conversion pod, as the source is VirtualBox, it's unsupported source, need to add the validate message in Plan page (E.g. controller/plan/validation.go) to let user notice this before the migration.

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

MTV 2.9.0 (forklift-fbc-prod-v418:on-pr-16546d253dda4fc8d8b838f0703040f30a985cf0) with CNV 4.18.7

How reproducible:

Always

Steps to Reproduce:

1) Create a migrate plan to migrate VM: "Home Assistant" from ova file: https://github.com/home-assistant/operating-system/releases/download/15.2/haos_ova-15.2.ova

2) The plan is "Ready for migration" without warn message for the unsupported ova source (VirtualBox)

3) The plan hit error in conversion pod as below, more details in attached file: ova-test-e6d1c736ab8bc0db1332091873ae43805964-9pspx-virt-v2v.log 

Actual results:

In step2: Plan without warn message for unsupported OVA source
In step3: Plan failed

Expected results:

In step2: Add warn message for unsupported OVA source