roles/nginx: Add nginx signing key id to apt_key task

When you give Ansible the key id it will check if the key exists
before trying to download and add it. I got the long fingerprint
from `sudo apt-key finger`.

roles/nginx/tasks/main.yml

@@ -1,6 +1,6 @@
 ---
 - name: Add nginx.org apt signing key
-  apt_key: url=https://nginx.org/keys/nginx_signing.key state=present
+  apt_key: id=0x573BFD6B3D8FBC641079A6ABABF5BD827BD9BF62 url=https://nginx.org/keys/nginx_signing.key state=present
   tags: nginx, packages
 
 - name: Add nginx.org repo