fix a deadlock or sporadic crash during shutdown

include/aman/com/AircraftReporter.h

@@ -21,15 +21,14 @@ namespace aman {
      */
     class AircraftReporter {
     private:
-        bool          m_initialized;
-        zmq::socket_t m_socket;
+        std::unique_ptr<zmq::socket_t> m_socket;
 
         AircraftReporter() noexcept;
 
         template <typename T>
         bool setSocketKey(const std::string& key, T entry) {
             try {
-                this->m_socket.set(entry, key);
+                this->m_socket->set(entry, key);
                 return true;
             }
             catch (std::exception&) {