fix path for mariadb data dir for persistence

[OyvindLGjesdal]

I think there is a typo in volume path, someone may end up without persistence while using the example.

https://hub.docker.com/_/mariadb

The path could also be moved up one level

from:
https://hub.docker.com/_/mariadb

The -v /my/own/datadir:/var/lib/mysql:Z part of the command mounts the /my/own/datadir directory from the underlying host system as /var/lib/mysql inside the container, where MariaDB by default will write its data files.

[OyvindLGjesdal]

I believe the jdbc connector used in the current docker image (intranda/goobi-workflow:default-plugins) also has issues with mariadb 10.1, and understanding the jdbc url. I updated to 10.11 here which worked. It could also just be that I was confusing errors due to a missing volume.