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
Remove conditional for X-CS and X-Subdomain check for Vary:.

* X-CS and X-Subdomain should be added to Vary: header for 301s,
keeping in the spirit of idempotent URLs.

Change-Id: Ic830fe37f4ef1372bff0a7d6ac8cb41ff79339cd