Injects a `run_root` method into the registered root event plugins.

def _setup_root_plugins(self):
        """ Injects a `run_root` method into the registered root event plugins.
            """

        def run_root(_self, command):
            """ Executes a shell command as root.

                `command`
                    Shell command string.

                Returns boolean.
                """

            try:
                # get lock, so this plugin has exclusive access to command pipe
                self._rlock.acquire()

                # TODO: log root command for this plugin
                self._cmd_pipe.send_bytes('\x80'.join(['SHL', command]))
                res = self._cmd_pipe.recv_bytes()

                if res != 'TRM':  # sentinel value, shutdown
                    return res == 'OK'

            except (EOFError, IOError):
                pass

            finally:
                self._rlock.release()

            self.shutdown(skip_hooks=True)
            return False

        # inject method into each event plugin
        for plugin in registration.get_registered(event_hooks=True,
                                                  root_access=True):
            plugin.run_root = types.MethodType(run_root, plugin)