[Bug] ClientConnection's references are still held after closing

[BewareMyPower]

Search before asking

• I searched in the issues and found nothing similar.

Version

1a39e53

Minimal reproduce step

Run ./build/tests/pulsar-tests --gtest_filter='Pulsar/ReaderSeekTest.testHasMessageAvailableAfterSeekToEnd/0'

What did you expect to see?

No WARN logs

What did you see instead?

2026-03-17 20:12:43.384 WARN  [0x16bd9f000] ConnectionPool:79 | Connection still has 3 references after waiting for 5 seconds for [[::1]:50551 -> [::1]:6650]

Anything else?

It should be a regression introduced by #551

Are you willing to submit a PR?

• I'm willing to submit a PR!