Add registry prefix option

[saschagrunert]

This allows to pre-pull the images and running benchmarks against a
local registry.

Beside this, the succinct output for benchmarks seems more reasonable
to me, so we put it on per default.

[feiskyer]

the imageName may already contains the image registry, e.g. "gcr.io/cri-tools/test-image-1:latest". So adding another prefix may not work. I think we should parse the image first and replace the registry with TestContext.RegistryPrefix.

[saschagrunert]

I agree, I changed the implementation to parse the image name before. Since the parsing expects a fully qualified image name, we now fallback to the intial imageName if the parsing fails. If not, we split up the domain and replace it.

[saschagrunert]

Please take a look again, I had to change the benchmark images to be fully qualified to make the registry prefix replacement work.

[feiskyer]

Tests failed:

/home/travis/gopath/src/github.com/kubernetes-sigs/cri-tools/pkg/framework/framework.go:72
  SeccompProfilePath
  /home/travis/gopath/src/github.com/kubernetes-sigs/cri-tools/pkg/validate/security_context_linux.go:483
    should support seccomp unconfined on the container [AfterEach]
    /home/travis/gopath/src/github.com/kubernetes-sigs/cri-tools/pkg/validate/security_context_linux.go:529
    failed to pull image: rpc error: code = Unknown desc = invalid reference format
    Unexpected error:
        <*status.statusError | 0xc000401fb0>: {
            Code: 2,
            Message: "invalid reference format",
            Details: nil,
        }
        rpc error: code = Unknown desc = invalid reference format
    occurred

[saschagrunert]

I fixed the failing CI, in the end we would now need fully qualified images for every test. WDYT?

[feiskyer]

I fixed the failing CI, in the end we would now need fully qualified images for every test. WDYT?

Could we default to docker.io if the registry is not included in the image?

[saschagrunert]

Could we default to docker.io if the registry is not included in the image?

Yeah I think so, I will make docker.io/library the default prefix and if that not changes, then the tests should need no further adaption.

It's a bit tricky, sorry for all the different kind of approaches 😇

[feiskyer]

/lgtm
/approve

[k8s-ci-robot]

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