No default docker base image configuration in the config file

[anuragvij264]

No default docker base image is available in the config. It breaks the containerizing of service https://github.com/bentoml/BentoML/blob/c32c36da5f323e9bccc235c4385e302201c3e798/bentoml/configuration/default_bentoml.cfg#L23

To Reproduce

1. Use this above the service@bentoml.env(docker_base_image="bentoml/model-server:0.8.12-slim-py37")

Expected behavior

1. Using the commands give here https://docs.bentoml.org/en/latest/concepts.html#api-server-dockerization. It's not able to dockerize the service

Logs

Error: bentoml-cli containerize failed: manifest for bentoml/model-server:0.8.12-slim-py37 not found: manifest unknown: manifestunknown

Environment:

• OS: [e.g. MacOS 10.15.7]
• Python Version [e.g. Python 3.7.9]
• BentoML Version [e.g. BentoML-0.9.2]

[parano]

@anuragvij264 do you mean to use model-server:0.9.2-slim-py37? BentoML does not have 0.8.12 release

The config is supposed to be empty so it uses the default value.