We compile our own MariaDB packages, and all galera and wsrep files have been separated into a subpackage along with its dependencies and configuration files.
After upgrading from 10.1.14 to 10.1.16, mariadb server fails to start due to missing the galera_recovery script. From what I can gather in the systemd configuration, it could/should check for the existance of galera_recovery before attempting to run it.
As a workaround I could include the script in the server subpackage, but I am uncertain whether that would actually work since it might just error out due to other missing wsrep/galera files.
The cleanest way I think would be to only run the script if it exists, and otherwise assume galera is not activated. Possibly check for some other file(s) as well and return a warning if galera is present such that it can be activated but the recovery script is missing.