main: Improve comments on fprint manager creation

Explain why the manager creation is async better in both in the main file
and in the manager itself

src/main.c

@@ -191,8 +191,8 @@ int main(int argc, char **argv)
 	g_debug("Launching FprintObject");
 
 	/* create the one instance of the Manager object to be shared between
-	 * all fprintd users */
-	manager = fprint_manager_new(no_timeout);
+	 * all fprintd users. This blocks until all the devices are enumerated */
+	manager = fprint_manager_new (no_timeout);
 
 	/* Obtain the well-known name after the manager has been initialized.
 	 * Otherwise a client immediately enumerating the devices will not see

src/manager.c

@@ -174,7 +174,9 @@ fprint_manager_init (FprintManager *manager)
 				 manager,
 				 G_CONNECT_SWAPPED);
 
-	/* Prepare everything by enumerating all devices. */
+	/* Prepare everything by enumerating all devices.
+	 * This blocks the main loop until the existing devices are enumerated
+	 */
 	fp_context_enumerate (priv->context);
 
 	dbus_g_connection_register_g_object(fprintd_dbus_conn,