xenapi: rename hostname not working on windows

[Kashi Reddy]

Repro steps:
- start windows server
- user changes hostname

Expected:
- new hostname persists across reboot

Actual:
- hostname reverts to original name

Reason for issue:
- PV tools read the hostname in xenstore on every reboot
- after first boot the xenstore key is never update or removed

Fix
- Remove the hostname in first boot after network reset

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/37884

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/37884
Committed: http://github.com/openstack/nova/commit/f10279662a0775e6884bd1b58933752e6f982ca6
Submitter: Jenkins
Branch: master

commit f10279662a0775e6884bd1b58933752e6f982ca6
Author: Kashi Reddy <email address hidden>
Date: Fri Jul 19 16:04:57 2013 +0530

    Remove hostname param from XenApi after first boot

    Removes hostname param from XenApi after first boot.
    Hostname being present is causing PV tools to pick
    old hostname and revert the hostname changes.

    Fixes: bug #1203025
    Change-Id: I48d8e43addb8d6cd84ad160cd52427d47a31ff69