fixed clang-tidy errors

fixed clang compilation error and few clang-tidy issues

Tested:
- Code compiles, all unit tests are passing
- Number of reported clang-tidy issues decreased

Change-Id: Ie3f88db6e2dffb26ec6c56dbdc1ce5bad288dccd
Signed-off-by: Krzysztof Grobelny <krzysztof.grobelny@intel.com>
diff --git a/src/metric.cpp b/src/metric.cpp
index d8241b9..582e506 100644
--- a/src/metric.cpp
+++ b/src/metric.cpp
@@ -107,7 +107,8 @@
 class Metric::DataStartup : public Metric::CollectionData
 {
   public:
-    DataStartup(std::shared_ptr<details::CollectionFunction> function) :
+    explicit DataStartup(
+        std::shared_ptr<details::CollectionFunction> function) :
         function(std::move(function))
     {}