mariadb: Disable networking

We don't use it so it doesn't need to listen.

Signed-off-by: Florian Pritz <bluewind@xinu.at>

roles/mariadb/defaults/main.yml

 ---
 mariadb_skip_name_resolve: False
-mariadb_skip_networking: False
+mariadb_skip_networking: True
 
 mariadb_key_buffer_size: '16M'
 mariadb_max_allowed_packet: '16M'