Added dummy task to gather facts.

see https://serverfault.com/questions/638507/how-to-access-host-variable-of-a-different-host-with-ansible

keystone.yml

@@ -1,4 +1,8 @@
 ---
+- hosts: databases
+  name: Dummy to gather facts
+  tasks: []
+
 - hosts: keystone
   become: True
   roles: