fix(device-handler): make _maybe_retry_device_resync thread-safe

[3nprob]

A race-condition may render concurrent retry loops.

Use an actual Lock for guarding single access of device resyncing retrying.

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
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• Code style is correct
  (run the linters)

[sandhose]

Thanks for the fix! Is this an issue you encountered in production?

[3nprob]

Thanks for the fix! Is this an issue you encountered in production?

NP and ty for review!

I believe so but haven't reproduced.