This reduces the need to pull random images from docker.io, and should
greatly reduce the tendancy to hit their hourly rate-limit during
integration test runs.
TestImagePullSomePlatforms uses k8s.gcr.io/pause:3.2 so that it does not
see the content pulled by TestImagePullAllPlatforms. This image is
multi-arch, but not multi-os.
Signed-off-by: Paul "TBBle" Hampson <Paul.Hampson@Pobox.com>
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