minor clang-tidy fixes (#2213)

* clang-tidy: add const to member function

Signed-off-by: Rosen Penev <rosenp@gmail.com>

* clang-tidy: remove duplicate access specifier

Signed-off-by: Rosen Penev <rosenp@gmail.com>

app/actions.hpp

@@ -73,7 +73,7 @@ class Task {
     return bResult;
   }
 
-  bool binary() {
+  bool binary() const {
     return binary_;
   }
 

app/exiv2app.hpp

@@ -217,7 +217,6 @@ class Params : public Util::Getopt {
 
   Params();
 
- private:
   //! @name Helpers
   //@{
   int setLogLevel(const std::string& optarg);

samples/metacopy.hpp

@@ -22,7 +22,6 @@ class Params : public Util::Getopt {
   std::string read_;      //!< Source file
   std::string write_;     //!< Destination file
 
- public:
   /*!
     @brief Default constructor. Note that optstring_ is initialized here.
    */