change close_connection() to close_old_connections() per 1.8
diff --git a/xos/synchronizers/model_policy.py b/xos/synchronizers/model_policy.py
index c414586..2ad6966 100644
--- a/xos/synchronizers/model_policy.py
+++ b/xos/synchronizers/model_policy.py
@@ -113,7 +113,7 @@
            try:
 #               if db.connection:
 #                   db.connection.close()
-               db.close_connection()
+               db.close_old_connections()
            except:
                 logger.log_exc("XXX we failed to fix the failure")
         else: