quickbackup-percona always locks database

[shaneiseminger]

Would be great to have an option to enable --no-lock (and with it --safe-slave-backup) in backups. This is useful on busy servers where even a few seconds of read-locked tables is too much. Obviously this comes with some danger and should only be used where the binlog position is not needed (e.g. no async replication).

I ran across the need for this when running backups on a server where only system tables are MyISAM, but xtrabackup still read-locked everything for 30+ seconds, sometimes many minutes.