Make smtp test more robust

It may have ended up with changes still in the pipeline because
it uses the timer trigger.

Change-Id: Ieb46d7b5b7020e62e7d3baa704e3f75f9f87dca1
diff --git a/tests/test_scheduler.py b/tests/test_scheduler.py
index 9baa824..a7548c1 100755
--- a/tests/test_scheduler.py
+++ b/tests/test_scheduler.py
@@ -2131,6 +2131,7 @@
                         'tests/fixtures/layout-no-timer.yaml')
         self.sched.reconfigure(self.config)
         self.registerJobs()
+        self.waitUntilSettled()
         self.worker.release('.*')
         self.waitUntilSettled()