Fix some warnings by cppcheck

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: Icee0abe2e3130aa225db776efdcd47200eb38f8d
diff --git a/fault-monitor/fru-fault-monitor.hpp b/fault-monitor/fru-fault-monitor.hpp
index 5658218..923a0f9 100644
--- a/fault-monitor/fru-fault-monitor.hpp
+++ b/fault-monitor/fru-fault-monitor.hpp
@@ -45,7 +45,7 @@
     /** @brief constructs Add a watch for FRU faults.
      *  @param[in] bus -  The Dbus bus object
      */
-    Add(sdbusplus::bus::bus& bus) :
+    explicit Add(sdbusplus::bus::bus& bus) :
         matchCreated(
             bus,
             sdbusplus::bus::match::rules::interfacesAdded() +