I tried updating some mariadb installations from version 10.1.14 to version 10.1.16.
After restarting the daemon php-fpm and some other daemons (like apache mod_php) were no longer able to connect via unix socket.
Due to this problem I am not able to update to the latest version.
I did not try 10.1.15. Maybe this version is also affected.
The working permissions/contexts (as of 10.1.14)
The new but not working permissions/contexts (as of 10.1.16)
The error inside /var/log/audit/audit.log