LeveledCompactionStrategyTest.testCompactionProgress unit test fails sometimes

It appears the LeveledCompactionStrategyTest.testCompactionProgress test is sometimes failing on CI with the following error: http://cassci.datastax.com/job/trunk_utest/lastCompletedBuild/testReport/org.apache.cassandra.db.compaction/LeveledCompactionStrategyTest/testCompactionProgress/

According to CI history, it happened just recently but has already happened about ~30 runs ago so it's not a one off (it looks pretty are tbh though). It's worth a look.

Note that I just saw the failure on trunk but haven't checked other branches.