Fixing GCR Client for GKE images which used to be hosted under google-containers

[davidcollom]

This is related to #147

Actually https://gcr.io/v2/google-containers/kube-proxy-amd64/tags/list hasn't been updated for a long time because they switched to https://gke.gcr.io/v2/kube-proxy-amd64/tags/list and new images are published there.

Google has now stopped pushing to google-containers namespace and now all gcr URI's can have multiple nested paths or none what so ever under their own vanity domain (gke.gcr.io)

[hawksight]

Not sure if we have a release note but worth tagging this for the next minor version and mentioning incase people are still using it. I know they shouldn't but just deflect the issue back to GKE :)

[davidcollom]

Not sure if we have a release note but worth tagging this for the next minor version and mentioning incase people are still using it. I know they shouldn't but just deflect the issue back to GKE :)

@hawksight - We generate github release notes automatically on release 👍 - No one should be manually using these images, they're provided by GKE's system - I'd be very surprised if anyone is still on 1.18 of GKE 😬 as it was released 4 years ago! 🤯