Server hangs after too many connections in USER isolation level [Bug]

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)

### Search before asking

- [X] I have searched in the [issues](https://github.com/apache/kyuubi/issues?q=is%3Aissue) and found no similar issues.

### Describe the bug

If you run too many queries in parallel from one user in engine share level USER, the Kyuubi server gets stuck and does not release connections. The jobs just hang without finishing

### Affects Version(s)

1.7.0/1.7.1

### Kyuubi Server Log Output

_No response_

### Kyuubi Engine Log Output

_No response_

### Kyuubi Server Configurations

```yaml
kyuubi.engine.share.level=USER;
```

### Kyuubi Engine Configurations

_No response_

### Additional context

I can reproduce this issue by running a test plan in Jmeter with 30 threads(users) and ramp-up period - 600. Server restart helps

### Are you willing to submit PR?

- [ ] Yes. I would be willing to submit a PR with guidance from the Kyuubi community to fix.
- [X] No. I cannot submit a PR at this time.

Start by tracing Kyuubi server connection handling for the USER share level, then reproduce the hang with the reported JMeter setup of 30 threads and a 600-second ramp-up. Done means parallel queries complete normally and server connections are released without requiring a restart.

Written by the indexing model from the issue text.