[Postfix] use python bootstrapper to start POSTFIX container

data/conf/postfix/config_templates/mysql_relay_ne.cf.j2

@@ -0,0 +1,13 @@
+user = {{ DBUSER }}
+password = {{ DBPASS }}
+hosts = unix:/var/run/mysqld/mysqld.sock
+dbname = {{ DBNAME }}
+query = SELECT IF(EXISTS(SELECT address, domain FROM alias
+      WHERE address = '%s'
+        AND domain IN (
+          SELECT domain FROM domain
+            WHERE backupmx = '1'
+              AND relay_all_recipients = '1'
+              AND relay_unknown_only = '1')
+
+      ), 'lmtp:inet:dovecot:24', NULL) AS 'transport'