Target 'host' in 'evacuate' should not be the original server's host

[wingwj]

'Evacuate' function aims to help administrator/operator to evacuate servers if this compute node fails.

So we need to add a protection here, the target host should not be the original host.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/72554

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/72554
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=951bae39e704b04414ebb711b425631cf2d46be5
Submitter: Jenkins
Branch: master

commit 951bae39e704b04414ebb711b425631cf2d46be5
Author: wingwj <email address hidden>
Date: Tue Feb 11 12:09:03 2014 +0800

    Target host in evacuate can't be the original one

    'Evacuate' function aims to help administrator/operator to evacuate
    servers if this compute node fails.

    If no protection, the API returns a successful response,
    but the vm_state will be changed to ERROR after nova-compute started,
    due to the 'InstanceExists' exception raised from 'rebuild_instance()'.

    So we need to add verification here, the target host should not be the
    original host.

    Change-Id: Ic468cd57688b370a18cacfc6e0844a8201eb9ab3
    Closes-Bug: #1271821