Updated test to open plain text editor

With eclipse-platform/eclipse.platform.ui#2881,
.txt files are opened by default with more advanced "generic code
editor" so changed the file names to make sure they are not known by
content types catalog and so still opened with "old default" plain text
editor.

Fixes eclipse-jdt#2129

Author: iloveeclipse

org.eclipse.jdt.ui.tests/leaks/org/eclipse/jdt/ui/tests/leaks/JavaLeakTest.java

@@ -87,18 +87,18 @@ public class JavaLeakTest extends LeakTestCase {
 
 	@Test
 	public void testTextEditorClose() throws Exception {
-		IFile file= createTestFile("Test.txt");
+		IFile file= createTestFile("Test");
 		internalTestEditorClose(file, TextEditor.class, false);
 	}
 
 	@Test
 	public void testTextEditorCloseOneOfTwo() throws Exception {
-		IFile file1= createTestFile("Test1.txt");
+		IFile file1= createTestFile("Test1");
 		IEditorPart editor1= EditorUtility.openInEditor(file1);
 		assertEquals(editor1.getClass(), TextEditor.class);
 		assertInstanceCount(TextEditor.class, 1);
 
-		IFile file2= createTestFile("Test2.txt");
+		IFile file2= createTestFile("Test2");
 		IEditorPart editor2= EditorUtility.openInEditor(file2);
 		assertEquals(editor2.getClass(), TextEditor.class);
 		assertInstanceCount(TextEditor.class, 2);
@@ -116,7 +116,7 @@ public void testTextEditorCloseOneOfTwo() throws Exception {
 
 	@Test
 	public void testTextEditorCloseAll() throws Exception {
-		IFile file= createTestFile("Test.txt");
+		IFile file= createTestFile("Test");
 		internalTestEditorClose(file, TextEditor.class, true);
 	}