This review takes into account the following recommendations
* skip verbose option (use of log.level).
* use glob.glob to retrieve files matching rather that os.walk
* fix a bug in instanceBackupFS that did not return an already
existing backup
* add two functions to handle instance backup: clearInstanceBackupFS
(to remove one or all backups of an instance), _infoInstanceBackupFS
(just to keep path/pattern info of backup into a single routine)
* do not hard code '/tmp' as directory to store the backups. A new
optional argument 'backupdir' for createInstance, sets the attribute
'dirsrv.backupdir'. By default it takes '/tmp'. The caller of
createInstance (the test case), may provide 'backupdir' from an
environment variable (like it was done with $PREFIX)
https://fedorahosted.org/389/attachment/ticket/47584/0004-Ticket-47584-CI...