Define suites in defaults and add missing [community]

roles/rebuilderd/defaults/main.yml

 rebuilderd_domain: reproducible.archlinux.org
 rebuilderd_nginx_conf: /etc/nginx/nginx.d/rebuilderd.conf
-
 rebuilder_website_loc: /usr/share/webapps/rebuilderd-website
+
+suites:
+  - core
+  - extra
+  - testing
+  - community

roles/rebuilderd/tasks/main.yml

@@ -26,7 +26,4 @@
 
 - name: enable and start rebuilderd {{ item }} timer
   systemd: name=rebuilderd-sync@archlinux-{{ item }}.timer enabled=yes state=started
-  with_items:
-    - core
-    - extra
-    - testing
+  with_items: "{{ suites }}"