Flaky test: ClientTest.testCloseClient

[example failure](https://github.com/apache/pulsar-client-cpp/actions/runs/3797580369/jobs/6458643223)

```
FAILED TESTS (5/418):
743 ms: ./pulsar-tests ClientTest.testReferenceCount (try #1)
11653 ms: ./pulsar-tests ClientTest.testCloseClient (try #1)
9692 ms: ./pulsar-tests ClientTest.testCloseClient (try #2)
8242 ms: ./pulsar-tests ClientTest.testCloseClient (try #3)
8126 ms: ./pulsar-tests ClientTest.testCloseClient (try #4)
```

```
// ...
2022-12-29T01:22:46.5133298Z 2022-12-29 01:22:46.253 INFO [140291349905088] ConnectionPool:97 | Created connection for pulsar://localhost:6650
2022-12-29T01:22:46.5133649Z 2022-12-29 01:22:46.253 INFO [140291346781760] ClientConnection:387 | [[::1]:60292 -> [::1]:6650] Connected to broker
2022-12-29T01:22:46.5133967Z 2022-12-29 01:22:46.253 INFO [140291349905088] ClientImpl:516 | Closing Pulsar client with 0 producers and 0 consumers
2022-12-29T01:22:46.5134331Z 2022-12-29 01:22:46.254 INFO [140291330000448] ClientConnection:1602 | [[::1]:60292 -> [::1]:6650] Connection disconnected
2022-12-29T01:22:46.5134974Z 2022-12-29 01:22:46.254 ERROR [140291346781760] ClientImpl:183 | Error Checking/Getting Partition Metadata while creating producer on persistent://public/default/client-test-close-client-1672276958 -- NotConnected
2022-12-29T01:22:46.5135316Z 2022-12-29 01:22:46.254 INFO [140291330000448] ClientConnection:268 | [[::1]:60292 -> [::1]:6650] Destroyed connection
2022-12-29T01:22:46.5135700Z 2022-12-29 01:22:46.255 INFO [140291349905088] ClientConnection:190 | [ -> pulsar://localhost:6650] Create ClientConnection, timeout=10000
2022-12-29T01:22:46.5136036Z 2022-12-29 01:22:46.255 INFO [140291349905088] ConnectionPool:97 | Created connection for pulsar://localhost:6650
2022-12-29T01:22:46.5136486Z 2022-12-29 01:22:46.255 INFO [140291330000448] ClientConnection:387 | [[::1]:60300 -> [::1]:6650] Connected to broker
2022-12-29T01:22:46.5136808Z 2022-12-29 01:22:46.255 INFO [140291349905088] ClientImpl:516 | Closing Pulsar client with 0 producers and 0 consumers
2022-12-29T01:22:46.5137078Z [208/418] ClientTest.testCloseClient returned with exit code -11 (8126 ms)
```

It can be easily reproduced in local env by:

```bash
./tests/pulsar-tests --gtest_filter='ClientTest.testCloseClient' --gtest_repeat=20
```