volume-data-source-validator container image should be published for testing

[mkimuram]

volume-data-source-validator image is used for E2E tests in k/k, therefore it should be published.

[mkimuram]

@bswartz There is no document clearly describing this, but it seems that k8s.gcr.io/sig-storage/volume-data-source-validator:v0.1.0 is already available. Do documents need to be updated?

[maya-r]

It's also referenced in the following blog post. following along with it doesn't work as expected when the image isn't public

[bswartz]

That release is the alpha release. There will be a new, beta, release coming shortly, and a new blog entry referring to that version.

I'm happy to fix broken links in the existing published materials, but we can't use those old tags for the e2e test. Until we tag another version, we can only use canary images.

[mkimuram]

I think that it would be OK to wait for beta to update. However, for users who would like to test this feature as an alpha feature, it would be still helpful to update the yaml to use sig-storage/volume-data-source-validator:v0.1.0 (and hopefully also update README).