Looks like Docker changed how they're storing credentials in ~/.docker/config.json. Seems they've added support for keychains. We'll need to revisit how we encrypt/decrypt credentials in ~/.docker/config.json. Will open an issue for this.
Currently, if you provide a username without a password, it will prompt for a password. If you don't provide username/password, then it will attempt within the conductor container to decrypt them from ~/.docker/config.json.
Thanks for pointing out the new format of the config.json file.
--Chris