Checkmk Werk 15209: host_config: fix host attribute IPv6 address validation

ID: 15209 Title: host_config: fix host attribute IPv6 address validation Component: REST API Level: 1 Class: Bug fix Version: 2.2.0i1 Prior to this werk, the REST API failed with a 500 error if the user tried to query or create a host with a valid Host- or DNS name as Ipv6 address. This restriction also caused an error in the DCD as it is reliant on the the list all hosts endpoint. This werk resolves both issues.