KRB5: Allow writing multiple addresses to the kdcinfo plugin
    
    Turns the previous write_krb5info_file() function into a static function
    that writes whatever input it recevies. Adds a wrapper around it that
    accepts a list of strings, turns that into a newline-separated string
    which is then passed to the original function.
    
    Related:
    https://pagure.io/SSSD/sssd/issue/3291
    
    Reviewed-by: Sumit Bose <sbose@redhat.com>