DNS Locations: fix update-system-records unpacking error
    
    Method IPASystemRecords.records_list_from_node returns only list
    consists only from record names not tuple, which caused unpacking error
    
    https://fedorahosted.org/freeipa/ticket/6117
    
    Reviewed-By: Nikhil Dehadrai <ndehadra@redhat.com>