MariaDB: Disable the GSSAPI plugin
File /etc/my.cnf.d/auth_gssapi.cnf contains the line 

plugin-load-add=auth_gssapi.so


Comment it out and restart the service. The server should stop loading the plugin, it will make the errors go away. 

If you don't need the plugin at all, you can also uninstall MariaDB-gssapi packages

MariaDB-gssapi-server-10.1.19-1.el7.centos.x86_64
MariaDB-gssapi-client-10.1.19-1.el7.centos.x86_64