Fix CassandraStreamManagerTest.incrementalSSTableSelection flakiness

patch by Berenguer Blasi; reviewed by Benjamin Lerer for CASSANDRA-15825

The flakiness was caused by automatic compactions that were triggered by
the creation of the fourth SStable.

test/unit/org/apache/cassandra/db/streaming/CassandraStreamManagerTest.java

@@ -161,6 +161,9 @@ public class CassandraStreamManagerTest
     @Test
     public void incrementalSSTableSelection() throws Exception
     {
+        // CASSANDRA-15825 Make sure a compaction won't be triggered under our feet removing the sstables mid-flight
+        cfs.disableAutoCompaction();
+
         // make 3 tables, 1 unrepaired, 2 pending repair with different repair ids, and 1 repaired
         SSTableReader sstable1 = createSSTable(() -> QueryProcessor.executeInternal(String.format("INSERT INTO %s.%s (k, v) VALUES (1, 1)", keyspace, table)));
         SSTableReader sstable2 = createSSTable(() -> QueryProcessor.executeInternal(String.format("INSERT INTO %s.%s (k, v) VALUES (2, 2)", keyspace, table)));