[KYUUBI #403] FIx flaky test in ConnectionLevelSparkEngineSuite

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### _Why are the changes needed?_
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### _How was this patch tested?_
`ignore` -> `test`

Closes #403 from ulysses-you/flaky-test2.

d8aa6c7 [ulysses-you] empty
fd38e9c [ulysses-you] empty
2e5a7ee [ulysses-you] empty
444a526 [ulysses-you] fix

Authored-by: ulysses-you <ulyssesyou18@gmail.com>
Signed-off-by: ulysses-you <ulyssesyou18@gmail.com>

externals/kyuubi-spark-sql-engine/src/test/scala/org/apache/kyuubi/engine/spark/ShareLevelSparkEngineSuite.scala

@@ -41,7 +41,7 @@ abstract class ShareLevelSparkEngineSuite
     s"/kyuubi/${sharedLevel.toString}/${UUID.randomUUID().toString}"
   }
 
-  ignore("check discovery service is clean up with different share level") {
+  test("check discovery service is clean up with different share level") {
     withZkClient { zkClient =>
       assert(engine.getServiceState == ServiceState.STARTED)
       assert(zkClient.checkExists().forPath(namespace) != null)