Code review comment for lp:~sergei.glushchenko/percona-xtrabackup/ST-25967-2.0

This change is in xb_data_files_init, not in xb_delta_open_matching_space. Those srv_* values first inited in innodb_init_param. We should call xb_data_files_init once after calling innodb_init_param, and I can't see why we would need to do it more times. Another possible place to put this code in is innodb_init_param.