Fix error when creating TimeoutException

We need to have a valid format specifier. Currently this produces:

ValueError: unsupported format character 'w' (0x77) at index 50

[0] http://logs.openstack.org/94/561194/5/check/designate-base/401ff70/testr_results.html.gz

Change-Id: Ibb500c3ed26e23e7770901fa85e6e5bdbb15d741
diff --git a/designate_tempest_plugin/common/waiters.py b/designate_tempest_plugin/common/waiters.py
index 5c06623..ee59702 100644
--- a/designate_tempest_plugin/common/waiters.py
+++ b/designate_tempest_plugin/common/waiters.py
@@ -167,7 +167,7 @@
 
         if int(time.time()) - start >= client.build_timeout:
             message = ('Recordset %(recordset_id)s failed to reach '
-                       'status=%(status) within the required time '
+                       'status=%(status)s within the required time '
                        '(%(timeout)s s). Current '
                        'status: %(status_curr)s' %
                        {'recordset_id': recordset_id,