Redirect zerodot wikipedia webroot to mdot if OK

Previously, zero.wikipedia.org/ webroots on Wikipedia Zero
partner networks with only mdot languages being supported
were still being sent to a landing on lang.zero.wikipedia.org,
resulting in an unnecessary error. This patch tries to send
those users to the appropriate lang.m.wikipedia.org landing
location instead.

Change-Id: Ic99e2dcf8a005b87597bab1380ec0cd51f23a318
(cherry picked from commit dd78e2e01d14eabc65fe266ce14bcccf39980ddd)