fix: worker-poll tasks shouldn't block main loop

[vvcephei]

Description

Fixes a call to execute a task on the worker pool that still may block main event-loop
execution. See #7358 for more information.

Testing done

Just ran the tests.

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")

[ghost]

@confluentinc It looks like @vvcephei just signed our Contributor License Agreement. 👍

Always at your service,

clabot

[guozhangwang]

LGTM! And I also feel that we can just change it without adding more clunking tests.

[vvcephei]

Thanks, @guozhangwang ! It looks like I need a small tweak to the matcher in the JaasProviderTest. I'll fix it and then merge once there's a green build.