roles/nginx: Add fastcgi caching

Bypasses caching for logged in users (right now only for sessions
where the "wordpress_logged_in" cookie is set. Doubles the trans-
actions per second as measured by siege:

    $ siege -d1 -t1M -c50 https://mjanja.ch

Signed-off-by: Alan Orth <alan.orth@gmail.com>

roles/nginx/tasks/main.yml

@@ -15,6 +15,7 @@
   copy: src={{ item }} dest=/etc/nginx/{{ item }} mode=0644 owner=root group=root
   with_items:
     - extra-security.conf
+    - fastcgi_cache
     - nginx.conf
   notify:
     - reload nginx