Fixing TestBackupAndRestore::test_full_backup_and_restore_with_removed_users
    
    The test as it was, was testing the backup and restore based on previous
    backups and restore, not with an actual installation.
    
    Now, with a clear setup for each test, the test mentioned above will not
    fail to do a lookup (using the host command, in check_dns method) for
    the master domain.
    
    Reviewed-By: Christian Heimes <cheimes@redhat.com>