Fix global_state not disconnected after ray.shutdown

[jovany-wang]

What do these changes do?

Considering this script:

import ray
ray.init()
ray.shutdown()
ray.global_state.object_table()

It throws a ConnectionRefusedError error. Worse, _check_connected () will pass.

[AmplabJenkins]

Can one of the admins verify this patch?

[AmplabJenkins]

Test FAILed.
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[raulchen]

better put this in shutdown, because global_state isn't part of the worker

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[AmplabJenkins]

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[robertnishihara]

Suggested change

	ray.init()
	ray.init(num_cpus=0)

[robertnishihara]

Suggested change

	"""Disconnect this worker from the raylet and object store"""
	"""Disconnect this worker from the raylet and object store."""

[robertnishihara]

I'm surprised that Travis ran the Java tests.. it shouldn't have done that for this PR.

[AmplabJenkins]

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[robertnishihara]

Thanks @jovany-wang!