krb5_locator: Allow hostname in kdcinfo files
    
    Currently we support only IP addresses in kdcinfo files. We need
    to resolv eventual dns name and then we have to iterate trough
    list of addresses because hostname can be resolved that way, including
    IPv4 and IPv6 addresses.
    
    Resolves:
    https://pagure.io/SSSD/sssd/issue/3973
    
    Reviewed-by: Sumit Bose <sbose@redhat.com>