contint: support X-Forwarded-Proto for main site

The integration.wikimedia.org is going to be served by Varnish. Whenever
varnish terminates the https connection, it would query gallium over
HTTP so we dont want to redirect that to HTTPS or we end up in a loop.

Change-Id: I838cecb87b183a4092d1969aca570b73b3aeaefd