mariadb container name variable

mariadb container name variable is fixed in some places,
but in the defaults directory, mariadb container_name variable
is variable. If the mariadb container_name variable is changed
during deployment, it will not be assigned to container_name,
but a fixed 'mariadb' name.

Change-Id: Ie8efa509953d5efa5c3073c9b550be051a7f4f9b