Update volume-attachment API url in policies
Update volume-attachment API url in policies

Correct url is /servers/{server_id}/os-volume_attachments/{volume_id} [1].
'volume_id' and 'attachment_id' are conceptually different.

[1] https://developer.openstack.org/api-ref/compute/#show-a-detail-of-a-volume-attachment

Change-Id: Idbb165d8b695f5609306ddc678d0ad6fc559ab7e

klmitch/nova,mikalstill/nova,klmitch/nova,gooddata/openstack-nova,mahak/nova,rahulunair/nova,gooddata/openstack-nova,mahak/nova,gooddata/openstack-nova,openstack/nova,mikalstill/nova,rahulunair/nova,klmitch/nova,openstack/nova,openstack/nova,gooddata/openstack-nova,rahulunair/nova,mikalstill/nova,klmitch/nova,mahak/nova