update .dockercfg content to config.json

update the data format of .dockercfg to match the new docker config.json
format, which encapsulates all registry auth objects in an overall
"auths" object:

{
    "auths": {
        "reg.url": {
            "auth": "...=="
        }
    }
}

pkg/oc/cli/secrets/dockercfg.go

@@ -125,7 +125,9 @@ func (o CreateDockerConfigOptions) NewDockerSecret() (*api.Secret, error) {
 		Email:    o.EmailAddress,
 	}
 
-	dockerCfg := map[string]credentialprovider.DockerConfigEntry{o.RegistryLocation: dockercfgAuth}
+	dockerCfg := credentialprovider.DockerConfigJson{
+		Auths: map[string]credentialprovider.DockerConfigEntry{o.RegistryLocation: dockercfgAuth},
+	}
 
 	dockercfgContent, err := json.Marshal(dockerCfg)
 	if err != nil {