fix shutdown hang issue in connection queue

ChangeLog

@@ -1,6 +1,8 @@
 	* fix uTP edge case where udp socket buffer fills up
 	* fix nagle implementation in uTP
 
+	* fix race condition causing shutdown hang
+
 0.16.2 release
 
 	* fix permissions issue on linux whith noatime enabled for non-owned files

src/connection_queue.cpp

@@ -277,7 +277,8 @@ namespace libtorrent
 #endif
 
 		TORRENT_ASSERT(!e || e == error::operation_aborted);
-		if (e) return;
+		if (e && m_num_connecting == 0)
+			return;
 
 		ptime next_expire = max_time();
 		ptime now = time_now_hires() + milliseconds(100);