[fivetran] Use nonblocking socket for tokio

[bkirwi]

Motivation

Testdrive started failing for me locally due to this Tokio behaviour change: tokio-rs/tokio#7172

I'm unsure why this doesn't fail in CI... maybe a MacOS thing? I believe this is happening locally because I'm running the code in debug mode, and these assertions are debug-only for now. Anyways setting the option makes things work as expected.

Checklist

• This PR has adequate test coverage / QA involvement has been duly considered. (trigger-ci for additional test/nightly runs)
• This PR has an associated up-to-date design doc, is a design doc (template), or is sufficiently small to not require a design.
• If this PR evolves an existing $T ⇔ Proto$T mapping (possibly in a backwards-incompatible way), then it is tagged with a T-proto label.
• If this PR will require changes to cloud orchestration or tests, there is a companion cloud PR to account for those changes that is tagged with the release-blocker label (example).
• If this PR includes major user-facing behavior changes, I have pinged the relevant PM to schedule a changelog post.

[ParkMyCar]

Thanks!

[ggevay]

Thanks a lot for the fix, I've just run into this too!