Resize to zero disk flavor is not allowed

[Shuangtai Tian]

When old flavor's root_gb is not equal 0 and new flavor's root_gb is 0, the resize() in nova.compute.api will raise CannotResizeDisk.

https://github.com/openstack/nova/blob/master/nova/compute/api.py#L2368

    def resize(self, context, instance, flavor_id=None,
        if not flavor_id:
            LOG.debug("flavor_id is None. Assuming migration.",
                      instance=instance)
            new_instance_type = current_instance_type
        else:
            new_instance_type = flavors.get_flavor_by_flavor_id(
                    flavor_id, read_deleted="no")
            if (new_instance_type.get('root_gb') == 0 and
                current_instance_type.get('root_gb') != 0):
                reason = _('Resize to zero disk flavor is not allowed.')
                raise exception.CannotResizeDisk(reason=reason)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/106034

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/106034
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=80df9f5ec53cc71c1ec51a8590921ae5b776ec22
Submitter: Jenkins
Branch: master

commit 80df9f5ec53cc71c1ec51a8590921ae5b776ec22
Author: shuangtai <email address hidden>
Date: Thu Jul 10 19:58:58 2014 +0800

    Catch CannotResizeDisk exception when resize to zero disk

    When old flavor's root_gb is not equal 0 and new flavor's root_gb is 0,
    the resize() in nova.compute.api will raise CannotResizeDisk.

    Move up the new_instance_type check before using.

    Closes-Bug: #1340159

    Change-Id: I4abf93530cf919af50a88d6049019fb745547257