Flaky test cases in sentinel-demo-quarkus module

## Issue Description

Type: *bug report*

### Describe what happened (or what feature you want)

Flaky unstable test in `com.alibaba.csp.sentinel.demo.quarkus.GreetingResourceTest.testSentinelJaxRsQuarkusAdapter`:

```
ERROR] Tests run: 2, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 5.589 s <<< FAILURE! - in com.alibaba.csp.sentinel.demo.quarkus.GreetingResourceTest
[ERROR] testSentinelJaxRsQuarkusAdapter Time elapsed: 1.048 s <<< FAILURE!
java.lang.AssertionError:
1 expectation failed.
Expected status code <429> but was <200>.

at com.alibaba.csp.sentinel.demo.quarkus.GreetingResourceTest.testSentinelJaxRsQuarkusAdapter(GreetingResourceTest.java:45)

2020-07-22 03:10:31,055 INFO [io.quarkus] (main) Quarkus stopped in 0.027s
[INFO]
[INFO] Results:
[INFO]
[ERROR] Failures:
[ERROR] GreetingResourceTest.testSentinelJaxRsQuarkusAdapter:45 1 expectation failed.
Expected status code <429> but was <200>.
```

https://app.circleci.com/pipelines/github/alibaba/Sentinel/264/workflows/fd9ae813-fef6-416c-8a0d-65c55b95275d/jobs/2093

### Describe what you expected to happen

The test case should not fail.

Start with sentinel-demo-quarkus and GreetingResourceTest.java, especially testSentinelJaxRsQuarkusAdapter at line 45, then reproduce the failure through the linked CircleCI job or the module's test command. Trace why the request returns 200 instead of the expected 429, and consider the issue done when the test is stable and passes repeatedly.

Written by the indexing model from the issue text.