Fix rare test flake

[vlovich]

What does this PR do?

Deflakes a rare test flake

Motivation

Saw this false-positive test failure:

failures:
---- channels::shared_channel::test::shared_drop_cascade_drop_executor_reverse stdout ----
thread 'unnamed-67' (3258883) panicked at glommio/src/channels/shared_channel.rs:140:63:
called Option::unwrap() on a None value
thread 'channels::shared_channel::test::shared_drop_cascade_drop_executor_reverse' (3258791) panicked at glommio/src/channels/shared_channel.rs:944:20:
called Result::unwrap() on an Err value: Thread panicked { .. }
failures:
channels::shared_channel::test::shared_drop_cascade_drop_executor_reverse

Related issues

N/A

Additional Notes

Couldn't reproduce but Codex explained the issue. The fix seems sensible.

Checklist

[X] I have added unit tests to the code I am submitting
[X] My unit tests cover both failure and success scenarios
[] If applicable, I have discussed my architecture

[datadog-datadog-us1-prod]

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⚠️ Warnings

❌ Your PR has failed checks. Please review the issues below and take necessary action before merging.

🚦 2 Pipeline jobs failed

Rust | build — 🔧 Needs a code fix, caused by this PR

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Compilation error: no method named 'random_range' found for struct 'ThreadRng' in the current scope. Consider importing trait 'RngExt'.

Rust | test — 🔧 Needs a code fix, caused by this PR

View more details · View in GitHub Actions

15 failed tests due to unsupported operations with DMA file tests: EnhancedIoError { source: Os { code: 95, kind: Unsupported, message: "Operation not supported" }, op: "Reading" }

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Branch: deflake-test

Rust | build
Commit: 9a16d56a6dda601cb227e40474f03014de664a3d
Error (code / build):
Compilation error: no method named 'random_range' found for struct 'ThreadRng' in the current scope. Consider importing trait 'RngExt'.
CI job: https://github.com/DataDog/glommio/actions/runs/33825058181/job/100875822934

Rust | test
Commit: 9a16d56a6dda601cb227e40474f03014de664a3d
Error (code / test):
15 failed tests due to unsupported operations with DMA file tests: EnhancedIoError { source: Os { code: 95, kind: Unsupported, message: "Operation not supported" }, op: "Reading" }
CI job: https://github.com/DataDog/glommio/actions/runs/33825058181/job/100875823021

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