clang-tidy: Enable readability-make-member-function-const check

Finds non-static member functions that can be made const because the
functions don’t use this in a non-const way.

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: Iff3a367401d571f9fcff90539aaab59e2c66e627
diff --git a/test/test_item_updater.cpp b/test/test_item_updater.cpp
index c231654..58125c7 100644
--- a/test/test_item_updater.cpp
+++ b/test/test_item_updater.cpp
@@ -41,7 +41,7 @@
         utils::freeUtils();
     }
 
-    auto& GetActivations()
+    auto& GetActivations() const
     {
         return itemUpdater->activations;
     }
@@ -52,12 +52,12 @@
     }
 
     void onPsuInventoryChanged(const std::string& psuPath,
-                               const Properties& properties)
+                               const Properties& properties) const
     {
         itemUpdater->onPsuInventoryChanged(psuPath, properties);
     }
 
-    void scanDirectory(const fs::path& p)
+    void scanDirectory(const fs::path& p) const
     {
         itemUpdater->scanDirectory(p);
     }