Fetching files in the build phase

[hxietkg]

Reason for PR:
Current burrito is an empty burrito image, it downloads file in the run phase only, we need a burrito image with files already pulled. In this change a new ARG 'CONFIG_FILE' is added, which indicates the file list to be downloaded, we may pass an ARG to 'docker build':
docker build --build-arg CONFIG_FILE= ......

Issue Fixed:
N/A

Requirements

• Sqaush commits
• Documentation
• Tests

Notes:

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[jayunit100]

/lgtm