ZooKeeperHaServicesTest.testCloseAndCleanupAllDataWithUncle is unstable

08:26:51.737 [INFO] Running org.apache.flink.runtime.highavailability.zookeeper.ZooKeeperHaServicesTest
08:26:52.862 [INFO] Tests run: 23, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 8.01 s - in org.apache.flink.runtime.jobmaster.JobMasterTest
08:26:53.612 [INFO] Running org.apache.flink.runtime.highavailability.zookeeper.ZooKeeperRegistryTest
08:26:54.722 [ERROR] Tests run: 3, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 2.983 s <<< FAILURE! - in org.apache.flink.runtime.highavailability.zookeeper.ZooKeeperHaServicesTest
08:26:54.722 [ERROR] testCloseAndCleanupAllDataWithUncle(org.apache.flink.runtime.highavailability.zookeeper.ZooKeeperHaServicesTest)  Time elapsed: 0.067 s  <<< FAILURE!
java.lang.AssertionError: 

Expected: is null
     but: was <75,75,1553588814702,1553588814702,0,0,0,0,0,0,75
>
	at org.apache.flink.runtime.highavailability.zookeeper.ZooKeeperHaServicesTest.testCloseAndCleanupAllDataWithUncle(ZooKeeperHaServicesTest.java:160)