Don't allow the FQDN to match the domain on server installs

If server FQDN matches the domain name, the installation will succeed,
but DNS records will not work. If 'setup_dns: true' is used, there will
be no A record for the host, only a NS record, and the PTR record will
point to the domain name.

Based on: https://github.com/freeipa/freeipa/pull/6853
Related to: https://pagure.io/freeipa/issue/9003