Fix 2.2 eclipse-warnings

patch by Mick Semb Wever; reviewed by Benedict for CASSANDRA-15427

src/java/org/apache/cassandra/db/compaction/CompactionManager.java

@@ -844,6 +844,7 @@ public class CompactionManager implements CompactionManagerMBean
      *
      * @throws IOException
      */
+    @SuppressWarnings("resource")
     private void doCleanupOne(final ColumnFamilyStore cfs, LifecycleTransaction txn, CleanupStrategy cleanupStrategy, Collection<Range<Token>> ranges, boolean hasIndexes) throws IOException
     {
         assert !cfs.isIndex();

src/java/org/apache/cassandra/db/compaction/LeveledCompactionStrategy.java

@@ -215,6 +215,7 @@ public class LeveledCompactionStrategy extends AbstractCompactionStrategy
         return maxSSTableSizeInMB * 1024L * 1024L;
     }
 
+    @SuppressWarnings("resource")
     public ScannerList getScanners(Collection<SSTableReader> sstables, Range<Token> range)
     {
         Set<SSTableReader>[] sstablesPerLevel = manifest.getSStablesPerLevelSnapshot();

src/java/org/apache/cassandra/tools/SSTableExport.java

@@ -312,8 +312,7 @@ public class SSTableExport
             excludeSet = new HashSet<>(Arrays.asList(excludes));
 
         SSTableIdentityIterator row;
-        ISSTableScanner scanner = reader.getScanner();
-        try
+        try (ISSTableScanner scanner = reader.getScanner())
         {
             outs.println("[");
 
@@ -340,10 +339,6 @@ public class SSTableExport
             outs.println("\n]");
             outs.flush();
         }
-        finally
-        {
-            scanner.close();
-        }
     }
 
     /**