some APIs treat 412s as the conflict code.

[modular-magician]

it stands for 'invalid etag' in that context.

Fixes #7853

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Release Note Template for Downstream PRs (will be copied)

iam: fixed iam conflict handling so that optimistic-locking retries will succeed more often.

Derived from GoogleCloudPlatform/magic-modules#4277

[ghost]

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