Add test for postfix install on jenkins worker

playbooks/roles/jenkins_worker/tasks/test_platform_worker.yml

@@ -34,6 +34,10 @@
 # Assert that it was modified at least within the hour
       - "{{ testfile.stat.mtime }} - {{ edxvenv.stat.mtime }} < 3600"
 
+# Verify that postfix (mail server) is listening
+- wait_for: host={{ inventory_hostname }} port=25
+  delegate_to: localhost
+
 # Tear Down #
 - name: Remove test file
   file: path=testfile state=absent