container: support bind mounted db data directory and mysql config

roles/container/templates/mariadb.cnf.j2

@@ -0,0 +1,8 @@
+# {{ ansible_managed }}
+
+{% for section in docker_mariadb_config | dict2items %}
+[{{ section.key }}]
+{% for item in section.value | dict2items %}
+{{ item.key }} = {{ item.value }}
+{% endfor %}
+{% endfor %}