[Platform] More consistent entrypoints across different platforms

[terrytangyuan]

This PR makes the entrypoint consistent across different platforms. Previously both /bin/bash are apiserver are used.

[github-actions]

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[DarkLight1337]

IIRC the entrypoint is kept this way on purpose for ROCm. cc @hongxiayang

[terrytangyuan]

I'd love to understand the rationale behind this. IMO we should have consistent default behavior. This can be overridden at container execution time anyways.