Varnish: add German version of CentralAutoLogin

Spezial:Zentrale_automatische_Anmeldung URLs are getting hashed to
cp1065 and contention is causing requests to them occasionally fail.

For the period of Nov 26th-29th, those URLs currently account for
387.375 503s, i.e. ~48% of all 503s:

264244 http://de.wikipedia.org/w/index.php?title=Spezial:Zentrale_automatische_Anmeldung/start&type=script
123131 http://de.wikipedia.org/w/index.php?title=Spezial:Zentrale_automatische_Anmeldung/createSession&gu_id=0&type=script&proto=https

Set backend_random to those too, similarly to what we've done to the
English version of CentralAutoLogin URLs.

Change-Id: I24419f378dc0e9aacd5ff7dab9dda891d36084ff