Hit the API on an mdot subdomain instead of a desktop subdomain.

* Wikipedia Zero extension API eligibility check is on mdot for foreseeable future.
* API behavior generally the same otherwise, so mdot is okay instead of desktop URL.
* Other aspects of the system still use the originally provided desktop domain.

Change-Id: Ic35ebe02c1abfa11059b52b6cddf94a00f09727f