Remove unused strands in server examples

example/http/server/async/http_server_async.cpp

@@ -346,7 +346,6 @@ public:
 // Accepts incoming connections and launches the sessions
 class listener : public std::enable_shared_from_this<listener>
 {
-    boost::asio::io_service::strand strand_;
     tcp::acceptor acceptor_;
     tcp::socket socket_;
     std::string const& doc_root_;
@@ -356,8 +355,7 @@ public:
         boost::asio::io_service& ios,
         tcp::endpoint endpoint,
         std::string const& doc_root)
-        : strand_(ios)
-        , acceptor_(ios)
+        : acceptor_(ios)
         , socket_(ios)
         , doc_root_(doc_root)
     {