Fix correct variable expansion in includes only_if.

There's not need to run the complete include through the templating engine.
Several variables were not included before the conditional was evaluated.

lib/ansible/playbook.py

@@ -160,8 +160,7 @@ class PlayBook(object):
                 include_vars[k] = v
         inject_vars = play_vars.copy()
         inject_vars.update(include_vars)
-        included = utils.template_from_file(path, inject_vars, SETUP_CACHE, no_engine=True)
-        included = utils.parse_yaml(included)
+        included = utils.parse_yaml_from_file(path)
         for x in included:
             if len(include_vars):
                 x["vars"] = include_vars