Pull Docker hub public image 401

[lou-lan]

Describe the bug
Pull Docker hub public image 401.

{
    "level":"error",
    "ts":1570771094.5547218,
    "msg":"failed to execute build plan: execute stage: build stage 0: build node: do execute: execute step: get manifest: pull image index.docker.io/library/nginx:latest: pull manifest: http send error: GET https://index.docker.io/v2/library/nginx/manifests/latest 401: {"errors":[{"code":"UNAUTHORIZED","message":"authentication required","detail":[{"Type":"repository","Class":"","Name":"library/nginx","Action":"pull"}]}]}"
}

To Reproduce

$ cat Dockerfile
FROM nginx

$ cat config.yml
"xxx.xxx.xxx.xxx":
  ".*":
    security:
      tls:
        client:
          disabled: true
      basic:
        username: "*****"
        password: "****"
"index.docker.io":
  ".*":
    security:
      tls:
        client:
          disabled: false
        basic:
          username: ""
          password: ""

Expected behavior
Pull nginx image sucessed.

[yiranwang52]

Actually it seems like something changed on dockerhub...still debugging.