Add support for hypervisor type in IronicHostManager

Unlike the default HostManager the IronicHostManager doesn't pass
hypervisor attributes of the compute_node into the HostState.

Adding support for hypervisor_type makes it easy to use the
compute_capabilities filter in a combined Ironic/virt system
with a simple extra_specs value on flavors.

For completeness the following values are added:
hypervisor_type
hypervisor_version
hypervisor_version
cpu_info
supported_instances

Change-Id: I1c81bb9726597609c4e5918eb15b4f2a055e7912
Closes-Bug: #1370578
Merge "Add support for hypervisor type in IronicHostManager"