Do not mark HTTPS requests with X-CS header

Since http and https traffic is treated the same as http by varnish
and zero extension, there is no variance on X-Forwarded-Proto header,
even though there are very few (non in production) carriers that
properly identify and zero-rate SSL traffic. Hence, we shouldn't be
identifying HTTPS traffic with X-CS header until zero+ESI can properly
handle it.

Change-Id: I39b8e83d656fbf97bb3c8d61d7336ebeb0fa2ab8
Merge "Do not mark HTTPS requests with X-CS header" into production