Fix the index page option for single files

Just create an index page for single files when the -i option
is passed like expected.

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>

renderer/render-test-case

@@ -68,7 +68,8 @@ if '__main__' == __name__:
 
     if os.path.isfile(args.yaml_files):
         generate_test_case_page(args.yaml_files, directory)
-        index_files.append(args.yaml_files)
+        if args.index_page:
+            index_files.append(args.yaml_files)
     else:
         c = 0
         for root, _, files in os.walk(args.yaml_files):