Fixed testcase to use Adapter instead of interface

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/io/trunk@1714088 13f79535-47bb-0310-9956-ffa450edef68

Author: krosenvold

src/test/java/org/apache/commons/io/input/TailerTest.java

@@ -436,7 +436,7 @@ public void testIO335() throws Exception { // test CR behaviour
     /**
      * Test {@link TailerListener} implementation.
      */
-    private static class TestTailerListener implements TailerListener {
+    private static class TestTailerListener extends TailerListenerAdapter {
 
         // Must be synchronised because it is written by one thread and read by another
         private final List<String> lines = Collections.synchronizedList(new ArrayList<String>());