serve graphite.wikimedia.org via misc-varnish

Ineffectual without the corresponding DNS update, but can be safely pushed out.
Note that templates/varnish/graphite.inc.vcl.erb set custom beresp.ttls, but I
prefer to manage that in Nginx and Graphite themselves.

Change-Id: Ib750a9c0253eff0f21fea95e919a32d63c1d0753
Merge "serve graphite.wikimedia.org via misc-varnish" into production