Ticket #630 - The backend name provided to bak2db is not validated
    
    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.
    
    Reviewed by Rich (Thank you!!)
    
    https://fedorahosted.org/389/ticket/630