Comment 4 for bug 1809041

So this looks to me like we need to update the docker-registry relation to HAProxy so that it configures things in active/passive rather than active/active mode - i.e. any HAProxy sitting in front of docker-registry should only send traffic to one of the docker-registry backend unless that backend is down. This will mean we're not getting the load-spreading benefits of multiple docker-registry units, but should solve this issue.

Marking this as critical as it currently affects any deployment with more than one docker-registry unit and HAProxy infront of it.