style: drop redundant member initializers

- remove constructor member initializers that duplicate the default
  member initialization
- clang-tidy readability-redundant-member-init
  https://clang.llvm.org/extra/clang-tidy/checks/readability/redundant-member-init.html

fairmq/PluginManager.cxx

@@ -32,12 +32,9 @@ const std::string fair::mq::PluginManager::fgkLibPrefixAlt = "FairMQPlugin_";
 std::vector<boost::dll::shared_library> fair::mq::PluginManager::fgDLLKeepAlive =
     std::vector<boost::dll::shared_library>();
 
-fair::mq::PluginManager::PluginManager()
-    : fPluginServices()
-{}
+fair::mq::PluginManager::PluginManager() {}
 
 fair::mq::PluginManager::PluginManager(const vector<string>& args)
-    : fPluginServices()
 {
     // Parse command line options
     auto options = ProgramOptions();