Adding X-Subdomain and X-CS to HTTP 301 Vary: header for Zero traffic.

	* Current Vary header redirect does not include this.
	* Wrong redirects to [LANG_CODE].m.wikipedia.org may cause
	  unnecessary charges to Zero users.

Change-Id: I903d4db7d6e4da09c7ccd7f08d43ac5a59590ee7
Merge "Adding X-Subdomain and X-CS to HTTP 301 Vary: header for Zero traffic."