implement hypervisor_hostname extended SRV-ATTR for libvirt

[Dan Prince]

On libvirt the OS-EXT-SRV-ATTR:hypervisor_hostname extension always displays 'None':

We should implement get_hypervisor_hostname in the libvirt connection and make use of it to set 'hypervisor_hostname' so that this information is displayed correctly.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/7445

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/7445
Committed: http://github.com/openstack/nova/commit/cdcb64f045764017a7fba4d86207e2ec30a957f9
Submitter: Jenkins
Branch: master

commit cdcb64f045764017a7fba4d86207e2ec30a957f9
Author: Dan Prince <email address hidden>
Date: Tue May 15 10:54:13 2012 -0400

    Implement get_hypervisor_hostname for libvirt.

    Implements get_hypervisor_hostname so that the
    OS-EXT-SRV-ATTR:hypervisor_hostname extension can properly
    display this information when using libvirt.

    Fixes LP Bug #999729.

    Change-Id: I124d48ca352dc225f88999046f9d212ffb9e4c6e