fixed UPnP shutdown issue

ChangeLog

@@ -43,6 +43,7 @@
 	  incoming connection
 	* added more detailed instrumentation of the disk I/O thread
 
+	* fixed UPnP shutdown issue
 	* fixed UPnP DeletePortmapping issue
 	* fixed NAT-PMP issue when adding the same mapping multiple times
 	* no peers from tracker when stopping is no longer an error

src/connection_queue.cpp

@@ -179,7 +179,8 @@ namespace libtorrent
 #ifdef TORRENT_CONNECTION_LOGGING
 		m_log << log_time() << " " << free_slots() << std::endl;
 #endif
-		if (m_abort) return;
+		// if this is enabled, UPnP connections will be blocked when shutting down
+//		if (m_abort) return;
 
 		if (m_num_connecting >= m_half_open_limit
 			&& m_half_open_limit > 0) return;