Fix cppcheck warnings

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: If5d808b9cb3bc733e7e21d546247d745ac5e1bf8
diff --git a/src/journal.cpp b/src/journal.cpp
index 09f98aa..f77293e 100644
--- a/src/journal.cpp
+++ b/src/journal.cpp
@@ -22,7 +22,7 @@
 namespace monitoring
 {
 
-void JournalBase::operator()(Context ctx)
+void JournalBase::operator()(Context /* ctx */)
 {
     for (const auto& n : index)
     {