clang-tidy: Enable readability-convert-member-functions-to-static

This check finds non-static member functions that can be made
static because the functions don’t use this.
This check also triggers readability-static-accessed-through
-instance check as we are trying to access a static member
function through an instance.

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: I6efe76666f75fb4f65621796466d9347cea25d01
diff --git a/manager/lamptest/lamptest.hpp b/manager/lamptest/lamptest.hpp
index 5e312e2..ce7bae1 100644
--- a/manager/lamptest/lamptest.hpp
+++ b/manager/lamptest/lamptest.hpp
@@ -79,7 +79,7 @@
      * with the persisted lamp test indicator file so that there is no sign of
      * lamptest.
      */
-    void clearLamps();
+    static void clearLamps();
 
   private:
     /** @brief Timer used for LEDs lamp test period */
@@ -88,9 +88,6 @@
     /** @brief Reference to Manager object */
     Manager& manager;
 
-    /** DBusHandler class handles the D-Bus operations */
-    DBusHandler dBusHandler;
-
     /** @brief Pointer to Group object */
     Group* groupObj;
 
@@ -137,13 +134,13 @@
      *
      *  @return enumeration equivalent of the passed in string
      */
-    Layout::Action getActionFromString(const std::string& str);
+    static Layout::Action getActionFromString(const std::string& str);
 
     /** @brief Notify host to start / stop the lamp test
      *
      *  @param[in]  value   -  the Asserted property value
      */
-    void doHostLampTest(bool value);
+    static void doHostLampTest(bool value);
 
     /** @brief Get physical LED names from lamp test JSON config file
      *