Fix InvalidListPruneTest#testRecordCompactionState flaky test

Async flush thread is making the InvalidListPruneTest flaky.

testRecordCompactionState(org.apache.tephra.hbase.txprune.InvalidListPruneTest) Time elapsed: 17.396 sec <<< FAILURE!
java.lang.AssertionError: expected:<50> but was:<-1>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at org.junit.Assert.assertEquals(Assert.java:555)
at org.junit.Assert.assertEquals(Assert.java:542)
at