This reverts commit e6624676e0.
Since e6624676e0, during login, we started
normalizing `registry-1.docker.io` to `index.docker.io`. This means that
if a user logs in with `docker login -u [username]
registry-1.docker.io`, the user's credentials get stored in
credhelpers/config.json under `https://index.docker.io/v1/`.
However, while the registry code normalizes an image reference without
registry (`docker pull alpine:latest`) and image references explicitly for
`index.docker.io` (`docker pull index.docker.io/library/alpine:latest`)
to the official index server (`https://index.docker.io/v1/`), and
fetches credentials for that auth key, it does not normalize
`registry-1.docker.io`, which means pulling explicitly from there
(`docker pull registry-1.docker.io/alpine:latest`) will not use
credentials stored under `https://index.docker.io/v1/`.
As such, until changes are made to the registry/pull/push code to
normalize `registry-1.docker.io` to `https://index.docker.io/v1/`, we
should not normalize this during login.
Signed-off-by: Laura Brehm <laurabrehm@hey.com>