Update default.vcl

Added cloudflare
https://support.cloudflare.com/hc/en-us/articles/200169376-Can-I-use-benefits-with-CloudFlare-and-Varnish-


      # Remove has_js and CloudFlare/Google Analytics __* cookies.
      set req.http.Cookie = regsuball(req.http.Cookie, "(^|;\s*)(_[_a-z]+|has_js)=[^;]*", "");
      # Remove a ";" prefix, if present.
      set req.http.Cookie = regsub(req.http.Cookie, "^;\s*", "");