Docker Go Tests fail on commits to k3s-io branches

[dereknola]

Environmental Info:
When commits are made to branches in k3s-io, often in depedabot or other automated bot branches.

Describe the bug:

The new docker go tests see the "skew" test consistently fail, as the logic around "Determine parent branch" is does not handle commit branches.

Steps To Reproduce:
https://github.com/k3s-io/k3s/actions/runs/12038906686/job/33565935782?pr=11336

Expected behavior:
Skew test should find "master" or other "release-1.XX" branch as parent.

Actual behavior:
Skew test finds the branch it is currently on as parent

Additional context / logs:

[dereknola]

Validated on #11336 as working again.