XtraBackup test framework force to use original my.cnf during prepare

[Sergei Glushchenko]

innobackupex bash function always invoke innobackupex script with following options:

IB_ARGS="--defaults-file=${MYSQLD_VARDIR}/my.cnf --user=root \
--socket=${MYSQLD_SOCKET} --ibbackup=$XB_BIN"

which is incorrect in the case of prepare, when backup-my.cnf should be used (--defaults-file option overrides default backup-my.cnf).

This cause some problems when we want to test backup-my.cnf, or when default my.cnf and backup-my.cnf are not identical, for example when we deal with separate doublewrite file.

[Alexey Kopytov (akopytov)]

This was fixed in the linked branch by changing innobackupex so that $backup_dir/backup-my.cnf is always used on --apply-log (even if there's a defaults file specified on the command line).

I don't think there's much use in overriding backup-my.cnf on prepare. In rare cases when someone somewhere may want to do so, one can always replace or edit backup-my.cnf to override some parameters.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PXB-86