k8s e2e tests reference `vectorized/configurator:latest` instead of local image

[ivotron]

While analyzing if we can remove latest from the configurator docker image repo, we realized that doing so will break the e2e tests, since it's the default version used: https://github.com/redpanda-data/redpanda/blob/5bd42df31171939a7dc40dab736eede10e108af1/src/go/k8s/main.go#L70

ideally, the tests should reference the image that has just been built from the codebase. since the configurator is stable and doesn't change often, this is not a problem currently, but it's something that should be fixed to avoid false positives in CI