Added dry run to preference requirement test

[RoniKishner]

What this PR does / why we need it:
Added dry run to preference requirement test to reduce run time

Special notes for your reviewer:
discussed #287

Release note:

NONE

[kubevirt-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign lyarwood for approval. For more information see the Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[0xFelix]

Can you please add it to other tests where appropriate as well?

[lyarwood]

Can you please add it to other tests where appropriate as well?

@0xFelix thinking about this some more, while we do validate things fully in the admission webhooks at the moment there is a growing desire to move this logic into the controller to better support the eventual consistency.

[0xFelix]

@lyarwood In this case, we could do without using DryRun at all.