Tiny cleanup to use class's field and add comment

Author: idodeclare

opengrok-indexer/src/main/java/org/opengrok/indexer/index/IndexerParallelizer.java

@@ -250,10 +250,10 @@ private void createLazyHistoryRenamedExecutor() {
                 Executors.newFixedThreadPool(env.getHistoryRenamedParallelism()));
     }
 
-    private static class CtagsObjectFactory implements ObjectFactory<Ctags> {
+    private class CtagsObjectFactory implements ObjectFactory<Ctags> {
 
         public Ctags createNew() {
-            return CtagsUtil.newInstance(RuntimeEnvironment.getInstance());
+            return CtagsUtil.newInstance(env);
         }
     }
 }

opengrok-indexer/src/test/java/org/opengrok/indexer/util/CtagsUtilTest.java

@@ -33,6 +33,9 @@
 
 import java.util.List;
 
+/**
+ * Represents a container for tests of {@link CtagsUtil}.
+ */
 @ConditionalRun(CtagsInstalled.class)
 public class CtagsUtilTest {