sst xtrabackup-v2 did not clean undo log dir

If there is different directory for undo log and log group home

innodb_undo_directory = /mysqlc/mysqld_data/undo
innodb_log_group_home_dir = /mysqlc/mysqld_data/log

In wsrep_sst_xtrabackup-v2 line 773

                wsrep_log_info "Cleaning the existing datadir and innodb-data/log directories"
                find $ib_home_dir $ib_log_dir $DATA -mindepth 1 -regex $cpat -prune -o -exec rm -rfv {} 1>&2 \+

Did not clean the undo log directory. It will fail the sst when it try to overwrite undo log.

percona-xtrabackup.x86_64
2.2.6-5042.el7