add remove '/v1/' to try get the authcfg

If docker login registry not add the '/v1/', the docker will not save the '/v1/' to .dockercfg.
So push to the registry will not find the authcfg and the 'X-Registry-Auth' will not add to push request .

eg:

docker login https://quay.io
It will save {"https://quay.io":{"auth":"xxxxx","email":"xxxxx"}} to .dockercfg

And if push:
client.push("quay.io/xxx/xxx", stream=False, insecure_registry=True)
it will not get the record, so the 'X-Registry-Auth' will not add to the push request.