tubes: mangle service name into file description

The version of Gabble that Michael and Eike are using doesn't support
the Metadata interface that we're using to direct this channel to
LibreOffice.

Perhaps putting something magic into the mime type would be a better
temporary workaround but hey.

tubes/source/file-transfer-helper.c

@@ -917,7 +917,7 @@ ft_handler_populate_outgoing_request (EmpathyFTHandler *handler)
       NULL);
 
   if (priv->service_name != NULL)
-    tp_asv_set_string (priv->request, TP_PROP_CHANNEL_INTERFACE_FILE_TRANSFER_METADATA_SERVICE_NAME, priv->service_name);
+    tp_asv_set_string (priv->request, TP_PROP_CHANNEL_TYPE_FILE_TRANSFER_DESCRIPTION, priv->service_name);
 
   g_free (uri);
 }

tubes/source/manager.cxx

@@ -489,7 +489,7 @@ bool TeleManager::connect()
             tp_asv_new(
                 TP_PROP_CHANNEL_CHANNEL_TYPE, G_TYPE_STRING, TP_IFACE_CHANNEL_TYPE_FILE_TRANSFER,
                 TP_PROP_CHANNEL_TARGET_HANDLE_TYPE, G_TYPE_UINT, TP_HANDLE_TYPE_CONTACT,
-                TP_PROP_CHANNEL_INTERFACE_FILE_TRANSFER_METADATA_SERVICE_NAME, G_TYPE_STRING, getFullServiceName().getStr(),
+                TP_PROP_CHANNEL_TYPE_FILE_TRANSFER_DESCRIPTION, G_TYPE_STRING, getFullServiceName().getStr(),
                 NULL));
 
     if (!tp_base_client_register( pImpl->mpFileTransferClient, &pError))