add "tls=dane" test for postfix 3.11

As mentioned on the mailinglist, postfix3.11 will have a `tls=<foo>` field. Example:

```
Sep 30 23:05:38 amnesiac postfix/smtp[793146]: 01E12901F9D:
        to=[<postfix-users@postfix.org>](mailto:postfix-users@postfix.org), relay=list.sys4.de[45.90.5.195]:25,
        delay=5.4, delays=0.08/0.01/3.5/1.9, tls=dane, dsn=2.0.0, status=sent
        (250 2.0.0 Ok: queued as 4cbdb56t4MzPjfw)
```