I've just reinstalled ovirt 4.2 (ovirt-release42.rpm) on a clean CentOS 7.4 host, all went fine however

Now that the hosted engine is up, I've added a data storage domain but it looks like the next step that detects / promotes the new data domain to master isn't being triggered.

Hosted engine and data domain are on NFS storage, /var/log/messages is filling with these messages

journal: ovirt-ha-agent ovirt_hosted_engine_ha.agent.hosted_engine.HostedEngine.config ERROR Unable to identify the OVF_STORE volume, falling back to initial vm.conf. Please ensure you already added your first data domain for regular VMs

I ran into the same issue when I imported an existing domain.