fixed saving in config plugin

Saving worked, but did you log out everytime. Now it is checked if the
auth mechanism was actually changed before assuming the login is
invalid.

lib/plugins/config/admin.php

@@ -65,8 +65,7 @@ class admin_plugin_config extends DokuWiki_Admin_Plugin {
         // save state & force a page reload to get the new settings to take effect
         $_SESSION['PLUGIN_CONFIG'] = array('state' => 'updated', 'time' => time());
         $this->_close_session();
-        header("Location: ".wl($ID,array('do'=>'admin','page'=>'config'),true,'&'));
-        exit();
+        send_redirect(wl($ID,array('do'=>'admin','page'=>'config'),true,'&'));
       }
 
       $this->_close_session();

lib/plugins/config/settings/extra.class.php

@@ -64,7 +64,7 @@ if (!class_exists('setting_authtype')) {
     		// reject disabled plugins
     		if ($plugin_controller->isdisabled($input)) {
 	    		$this->_error = true;
-	    		msg('Auth type ' . $input . ' is disabled.');
+	    		msg('Auth type ' . $input . ' is disabled.', -1);
 	    		return false;
     		}
 
@@ -74,21 +74,24 @@ if (!class_exists('setting_authtype')) {
 	    	// @TODO: throw an error in plugin controller instead of returning null
 	    	if (is_null($auth_plugin)) {
 	    		$this->_error = true;
-	    		msg('Cannot load Auth Plugin "' . $input . '"');
+	    		msg('Cannot load Auth Plugin "' . $input . '"', -1);
 	    		return false;
 	    	}
 
 	    	// verify proper instanciation (is this really a plugin?) @TODO use instanceof? impement interface?
 	    	if (is_object($auth_plugin) && !method_exists($auth_plugin, 'getPluginName')) {
 	    		$this->_error = true;
-				msg('Cannot create Auth Plugin "' . $input . '"');
+				msg('Cannot create Auth Plugin "' . $input . '"', -1);
 	    		return false;
 	    	}
     	}
 
-    	msg('Successfully changed auth system. Please re-login.');
-    	auth_logoff();
-
+        // did we change the auth type? logout
+        global $conf;
+        if($conf['authtype'] != $input) {
+    	    msg('Authentication system changed. Please re-login.');
+    	    auth_logoff();
+        }
     	return true;
     }
   }