controller: Add parameter for maximum log level to initiate/terminate_*()

Previously, the logger installed by the controller always announced
LEVEL_PRIVATE(4), which produced completely useless logging calls with
the common clients (vici/stroke) whose default log level is LEVEL_CTRL(1).
This can produce quite some overhead if there are e.g. a lot of concurrent
initiate() calls.

src/charon-cmd/cmd/cmd_connection.c

@@ -439,7 +439,7 @@ static job_requeue_t initiate(private_cmd_connection_t *this)
 	child_cfg = create_child_cfg(this, peer_cfg);
 
 	if (charon->controller->initiate(charon->controller, peer_cfg, child_cfg,
-								controller_cb_empty, NULL, 0, FALSE) != SUCCESS)
+				controller_cb_empty, NULL, LEVEL_SILENT, 0, FALSE) != SUCCESS)
 	{
 		terminate(pid);
 	}