`TestConfigController` is flaky

## Flaky Test

### Which jobs are failing
```
2024-04-08T03:05:00.1294129Z === RUN TestResourceManagerSuite/TestConfigController
2024-04-08T03:05:00.1294911Z resource_manager_command_test.go:71:
2024-04-08T03:05:00.1295979Z Error Trace: /home/runner/work/pd/pd/tools/pd-ctl/tests/resourcemanager/resource_manager_command_test.go:71
2024-04-08T03:05:00.1297585Z /home/runner/work/pd/pd/tools/pd-ctl/tests/resourcemanager/resource_manager_command_test.go:76
2024-04-08T03:05:00.1298338Z Error: Received unexpected error:
2024-04-08T03:05:00.1299117Z invalid character 'G' looking for beginning of value
2024-04-08T03:05:00.1299759Z Test: TestResourceManagerSuite/TestConfigController
2024-04-08T03:05:00.1300271Z --- FAIL: TestResourceManagerSuite (50.13s)
2024-04-08T03:05:00.1300858Z --- FAIL: TestResourceManagerSuite/TestConfigController (0.00s)
2024-04-08T03:05:00.1301280Z FAIL
2024-04-08T03:05:00.1301523Z coverage: [no statements]
2024-04-08T03:05:00.1302017Z FAIL github.com/tikv/pd/tools/pd-ctl/tests/resourcemanager 50.279s
```

### CI link
https://github.com/tikv/pd/actions/runs/8593935349/job/23546210799?pr=8033

### Reason for failure (if possible)

### Anything else