Fix some warnings by cppcheck

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: Icee0abe2e3130aa225db776efdcd47200eb38f8d
diff --git a/serialize.hpp b/serialize.hpp
index 23cffa2..71de987 100644
--- a/serialize.hpp
+++ b/serialize.hpp
@@ -21,7 +21,7 @@
 class Serialize
 {
   public:
-    Serialize(const fs::path& path) : path(path)
+    explicit Serialize(const fs::path& path) : path(path)
     {
         restoreGroups();
     }