basic-system/network: Use ansible_hostname instead of inventory_hostname

The latter one is not always a non-qualified name, in AStA it is a FQDN.

basic-system/tasks/network.yml

@@ -21,7 +21,7 @@
 
 - name: ensure the hostname is not a fqdn
   hostname:
-    name: "{{ inventory_hostname }}"
+    name: "{{ ansible_hostname }}"
   when: not dns_hostname_fqdn
   notify:
     - gather network facts once again