Hi umarzuki,
It seems like MariaDB’s system tables are not compatible with Percona XtraDB Cluster. I would advise instead to reload your dump of all the data from mysqldump, but do not include the mysql database.
Using your existing mysqldump file (if you have the latest one), use an open source tool - mysqldumpsplitter, to ‘split’ the dump file and only extract the databases you need to reload to the new cluster.
[url]https://github.com/kedarvj/mysqldumpsplitter[/url]
You could try to do an ALTER TABLE on mysql.proc and see if that works.