Revert "varnish: remove .{wap,mobile}. rewrites/redirects"

*.mobile.wikipedia.org gets hits from Googlebot and Bingbot.
301s wouldn't hurt them but let's revert that for now until
we understand why is that the case.

This partially reverts commit 745a20764b6f130a6ffec676e1d7f9756ce87551.

Change-Id: I74bab7704b02e0c1a5c5f1f12ad1d250e6f8d92e