Please review: [389 Project] #630: The backend name provided to bak2db is not validated

[Noriko Hosoi]

https://fedorahosted.org/389/ticket/630

https://fedorahosted.org/389/attachment/ticket/630/0001-Ticket-630-The-ba...

  Bug description: backend instance name was not validated correctly.
  When a given backend instance name was not valid, the instance name
  was ignored and the utility restored all instances, which was a default
  behaviour of the restore -- bak2db.

  Fix description: This patch adds the code to check the backend instance
  name.  If there is no backend instance, the restore request is ignored.
  In addition, it enhanced the back up path validation, as well.

  There was another bug found in the restore/bak2db.  The backend instance
  name is supposed to be case insensitive, but the case was not ignored.
  The bug was fixed, too.