osp_cluster_dns_server must be an IP address instead of a DNS name

[ericzolf]

According to https://docs.ansible.com/ansible/latest/collections/community/general/nsupdate_module.html the server parameter must be an IPv4 or v6 address. It used to work nevertheless as long as dnspython was below 2.0 but has stopped working since then, failing as e.g. described at https://ask.csdn.net/questions/1895695

The best would be probably to do a reverse resolution before applying the parameter osp_cluster_dns_server in case it doesn't look like an IP address.