[Client] disable auto init for get_runtime_context()

[mwtian]

Why are these changes needed?

ray.get_runtime_context() is sometimes called without Ray initialized, to test if the logic is indeed running with Ray. It seems we should not auto initialize Ray from calling this API.

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[ckw017]

For context, where is get_runtime_context used to test if the logic is on ray?

[ijrsvt]

LGTM! This makes sense :)

Did not realize this function was useful before Ray started.

[mwtian]

LGTM! This makes sense :)

Did not realize this function was useful before Ray started.

Me neither.

[jjyao]

Hi @mwtian, do you still have context on this PR. Why do we want to disable auto-init for get_runtime_context()?

[mwtian]

Hi @jjyao! I don't remember the details anymore other than what is in the PR description. I think get_runtime_context() was used just for detecting if a piece of code is running inside Ray client or cluster. And the logic can run without Ray, so it should not try to start Ray itself. I'm not sure if this use case still exists.