Rewrite nova compute_node hostnames

https://bugs.launchpad.net/grenade/+bug/1160072 was too simplistic to
correct the compute node name changes, we need to append the value
of dhcp_domain to the hypervisor_hostname column of compute_nodes.

Bug 1160999

Change-Id: I7c23cf8dae4a1fafb498124aca9e3fe0b857e563
Merge branch 'node-name-redux' into dt-test