Add explicit keyword to 1 arg constructors

The cppcheck tool complains about it otherwise.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: Id977a6c349b0b49354b52ac994ea7742e0a39307
diff --git a/control/json/utils/modifier.hpp b/control/json/utils/modifier.hpp
index 8959203..92fdb70 100644
--- a/control/json/utils/modifier.hpp
+++ b/control/json/utils/modifier.hpp
@@ -80,7 +80,7 @@
      *
      * @param[in] jsonObj - The JSON config object
      */
-    Modifier(const json& jsonObj);
+    explicit Modifier(const json& jsonObj);
 
     /**
      * @brief Performs the operation