Fix data race in timers

[antaljanosbenjamin]

Fixes #5082.

[confluent-cla-assistant[bot]]

:tada: All Contributor License Agreements have been signed. Ready to merge.
:white_check_mark: antaljanosbenjamin
_{Please push an empty commit if you would like to re-run the checks to verify CLA status for all contributors.}

[emasab]

/sem-approve

[antaljanosbenjamin]

Done.

[emasab]

/sem-approve

[antaljanosbenjamin]

@emasab do I need to do anything to get this merged or just wait?

[antaljanosbenjamin]

@emasab I feel like the merge is close. Can I do anything to help you with it?