no image cache tests for VMware Hyper

[Yaguang Tang]

no instance image file cache tests for VMware Hyper, we need to test linked_clone code logic .

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/46896

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/46896
Committed: http://github.com/openstack/nova/commit/b3a012e958a0fcf5b04ba470b194bc03a48673ce
Submitter: Jenkins
Branch: master

commit b3a012e958a0fcf5b04ba470b194bc03a48673ce
Author: Yaguang Tang <email address hidden>
Date: Tue Sep 17 15:47:51 2013 +0800

    Add linked clone related unit tests for VMware Hyper

    Test image file is cached when linked clone is enabled, and image file
    is downloaded and stored to instance dir directly when it's disabled.

    Fix bug #1226450

    Change-Id: I90f940de3de19a41b122e098d6788a5652287605