Fix logout link HTML.

<a id="logout" href=/projects/owncloud/core/index.php?logout=true>

lib/private/user.php

@@ -325,7 +325,7 @@ class OC_User {
 			return $backend->getLogoutAttribute();
 		}
 
-		return "href=" . link_to('', 'index.php') . "?logout=true";
+		return 'href="' . link_to('', 'index.php') . '?logout=true"';
 	}
 
 	/**