roles/certbot: Add some task tags

The *install* tag is applied to any task that installs a package.

The *user* tag is applied to any task that creates an OS user or group.

The *group* tag is applied to any task that creates an OS user group.

roles/certbot/tasks/main.yml

@@ -2,11 +2,16 @@
   package:
     name=certbot
     state=present
+  tags:
+  - install
 
 - name: ensure certbot group exists
   group:
     name=certbot
     system=yes
+  tags:
+  - group
+  - user
 - name: ensure certbot user exists
   user:
     name=certbot
@@ -15,6 +20,8 @@
     home=/var/lib/letsencrypt
     createhome=no
     state=present
+  tags:
+  - user
 
 - name: ensure certbot data directory exists
   file: