Fixup multiple model DS tests

[muellerzr]

What does this PR do?

Fixes failures on DS tests wrt multiple models.

TL;DR:

1. Need to remember to call AcceleratorState.reset_state() when we want to do things in concurrent different configurations (such as the multiple ds model configuration tests that actually do things)
2. Still need patch_environment to properly setup everything, otherwise we end up with failures when running the entire DS suite at once.

Fixes our tests & deepspeeds PR's from failing

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@SunMarc

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[SunMarc]

Thanks for fixing ! Make sense !