Add e2e upgrade tests

[makkes]

What would you like to be added: End-to-end test verifying upgrade behaviour between two different kubefed versions.

Why is this needed:

• Follow-up to Transition from apiextensions.k8s.io/v1beta1 to apiextensions.k8s.io/v1 #1296
• These tests could (should?) be run on each PR to ensure existing kubefed clusters don't break with a certain change.

/kind feature

[hectorj2f]

I might take care of this test ;).

[fejta-bot]

Issues go stale after 90d of inactivity.
Mark the issue as fresh with /remove-lifecycle stale.
Stale issues rot after an additional 30d of inactivity and eventually close.

If this issue is safe to close now please do so with /close.

Send feedback to sig-contributor-experience at kubernetes/community.
/lifecycle stale

[hectorj2f]

@makkes We added a test to upgrade from a previous image to the latest in master.

[makkes]

/remove-lifecycle stale

[makkes]

@hectorj2f would you mind linking it here and closing the issue then, please? Thanks!

[hectorj2f]

@makkes it was added here 8a435bc.