def action_conf(self, ctxt, action_class, action_name, config, step_addr):
return config<EOL>
A modifier hook function.  This is called in priority order prior
to initializing the ``Action`` for the step.  This allows a
modifier to alter the configuration to be fed to the action.

:param ctxt: The context object.
:param action_class: The ``Action`` subclass the modifier is
                     modifying.  This method should not
                     attempt to initialize the action.
:param action_name: The name of the action.
:param config: The configuration for the action.  This may be
               a scalar value (e.g., "run: command"), a list,
               or a dictionary.  If the configuration provided
               is invalid for the action, a ``ConfigError``
               should be raised.
:param step_addr: The address of the step in the test
                  configuration.  Should be passed to the
                  ``ConfigError``.

:returns: The configuration for the action, optionally
          modified.  If the configuration is not modified,
          ``config`` must be returned unchanged.  The default
          implementation of this method does so.