Registry aws go 1 8 fix

Fixes: https://gitlab.com/gitlab-org/omnibus-gitlab/issues/2350

I have forked docker distribution here: https://gitlab.com/twk3/docker-distribution and updated the aws-sdk-go dependency, using the release/2.6 branch. I updated it to the same version that they are using in master, to ship in the 2.7 release. Which is aws-sdk-go 1.6.12

My change is in the https://gitlab.com/twk3/docker-distribution/tree/bump-aws-version branch

1. We should move my fork into a gitlab group so more than just I have access (@marin I don't have access to do this)
2. We need to then also mirror it to dev
3. Update this MR with the new sources