Automatic merge from submit-queue

e2e-runner: Fix the logic of pulling GCI builtin version of k8s

Apparently setting JENKINS_PUBLISHED_VERSION didn't work because it only worked
with `ci/latest`, `release/latest-1.3` or the like, whereas we wanted to pull
specific versions like `release/v1.3.3`. Added a function
`fetch_gci_version_tars` instead.

@spxtr Can you review? Hopefully this should get our QA tests passing.