upnp: fix shutdown issues

GitLab: #21
GitLab: #28
Change-Id: I1c8e0ba00139b516ab964f8e0be76b571bd47534
diff --git a/include/upnp/upnp_context.h b/include/upnp/upnp_context.h
index ead135f..9941e3b 100644
--- a/include/upnp/upnp_context.h
+++ b/include/upnp/upnp_context.h
@@ -318,6 +318,7 @@
 
     // Shutdown synchronization
     bool shutdownComplete_ {false};
+    bool shutdownTimedOut_ {false};
 };
 
 } // namespace upnp