roles/mariadb: Only create users on 127.0.0.1 and ::1

A few months ago I disabled hostname lookups so only IP addresses
work now anyways.

roles/mariadb/tasks/main.yml

@@ -34,10 +34,8 @@
 - name: Update MariaDB root password for all root accounts
   mysql_user: name=root host={{ item }} password={{ mariadb_root_password }} login_unix_socket={{ mariadb_login_unix_socket }}
   loop:
-    - "{{ inventory_hostname }}"
     - 127.0.0.1
     - ::1
-    - localhost
   tags: mariadb
 
 - name: Create .my.conf file with root credentials