wrep_sst_common: Setting "-c ''" for my_print_defaults just takes no values from config at all. $MY_PRINT_DEFAULTS is already set at the top of the script to have --defaults-file and --defaults-extra-file. If WSREP_SST_OPT_CONF if set to "--defaults-file=/etc/my.cnf --defaults-extra-file=/etc/my.extra.cnf", then "my_print_defaults -c "" --defaults-file=/etc/my.cnf" succeeds, but if WSREP_SST_OPT_CONF is empty - no default values are taken at all.
wsrep_sst_xtrabackup-v2: innobackupex does not support --defaults-extra-file, so ${WSREP_SST_OPT_CONF} cannot be used as an argument, it has been changed to ${WSREP_SST_OPT_DEFAULT}. Removed --defaults-file= from INNOMOVE line, because WSREP_SST_OPT_CONF already includes it (INNOBACKUP was fine, INNOMOVE - not).