AbstractEventStream.nextThreadName race condition

[Carter Kozak]

Hello,

I noticed a race in AbstractEventStream.nextThreadName which can result in unintended thread names.
I've created a PR[1] with a proposed fix, but I don't have permissions to create a ticket for it. Hoping to
find someone willing to help here. Please let me know if there are additional steps I need to take.

1. https://github.com/openjdk/jdk/pull/1871

Thanks,
Carter Kozak