KafkaSupervisorTest.testCheckpointForInactiveTaskGroup transient failures

[himanshug]

from build log..

testCheckpointForInactiveTaskGroup[numThreads = 1](io.druid.indexing.kafka.supervisor.KafkaSupervisorTest)  Time elapsed: 60.007 sec  <<< ERROR!
java.lang.Exception: test timed out after 60000 milliseconds
	at io.druid.indexing.kafka.supervisor.KafkaSupervisorTest.testCheckpointForInactiveTaskGroup(KafkaSupervisorTest.java:2119)

[jihoonson]

Please check #6207.

[leventov]

Superseded by #6296.