Race condition with `Attestor`s?

## Summary

> If so, what happens if some other thread also writes to `/dev/attestation/user_report_data` before we read from `/dev/attestation/quote`?

_Originally posted by @thanethomson in https://github.com/informalsystems/cycles-quartz/pull/139#discussion_r1700655304_

Start with the discussion in pull request 139 and trace the code that writes to /dev/attestation/user_report_data before reading /dev/attestation/quote. Determine whether concurrent Attestor operations can interfere, and define a reproducible test or other evidence that establishes the expected behavior.

Written by the indexing model from the issue text.