Percona-cluster charm always deploys percona-cluster with 'innodb-file-per-table' turned off

[Mario Splivalo]

By default Percona's XtraDB Cluster is installed with innodb_file_per_table turned off.

Having innodb_file_per_table not set/enabled will put all the innodb tables into one huge ibdata file that resides inside mysql data directory. That has several negative consequences, two major of them are:

- there is absolutely no way (other than full dump/import of the datase) to shrink the on-disk footprint even if you delete/drop all the databases
- innobackupex is fairly slow as it can't start copying files in parallel - this also influences the speed of SST (State Snapshot Transfer, the way percona-cluster copies data over to the new nodes - it uses innobackupex underneath).

innodb_file_per_table should be configurable via juju config option for percona-cluster charm.