qcow image support broken in stable/folsom nova compute

Nova compute now tries to run qemu-img info on base images before it has downloaded them, resulting in an exception. If the image has already been cached, you won't see it. It looks like the bug was introduced by this security fix: https://bugs.launchpad.net/nova/folsom/+bug/1177830

This is the exception:

  File "/home/timjr/openstack/nova/app/nova/compute/manager.py", line 191, in decorated_function
    return function(self, context, *args, **kwargs)
  File "/home/timjr/openstack/nova/app/nova/compute/manager.py", line 839, in run_instance
    do_run_instance()
  File "/home/timjr/openstack/nova/app/nova/utils.py", line 803, in inner
    retval = f(*args, **kwargs)
  File "/home/timjr/openstack/nova/app/nova/compute/manager.py", line 838, in do_run_instance
    admin_password, is_first_time, instance)
  File "/home/timjr/openstack/nova/app/nova/compute/manager.py", line 529, in _run_instance
    self._set_instance_error_state(context, instance[\'uuid\'])
  File "/usr/lib64/python2.6/contextlib.py", line 23, in __exit__
    self.gen.next()
  File "/home/timjr/openstack/nova/app/nova/compute/manager.py", line 517, in _run_instance
    is_first_time, request_spec, filter_properties)
  File "/home/timjr/openstack/nova/app/nova/compute/manager.py", line 503, in _run_instance
    injected_files, admin_password)
  File "/home/timjr/openstack/nova/app/nova/compute/manager.py", line 756, in _spawn
    block_device_info)
  File "/home/timjr/openstack/nova/app/nova/exception.py", line 117, in wrapped
    temp_level, payload)
  File "/usr/lib64/python2.6/contextlib.py", line 23, in __exit__
    self.gen.next()
  File "/home/timjr/openstack/nova/app/nova/exception.py", line 92, in wrapped
    return f(*args, **kw)
  File "/home/timjr/openstack/nova/app/nova/virt/libvirt/driver.py", line 1099, in spawn
    admin_pass=admin_password)
  File "/home/timjr/openstack/nova/app/nova/virt/libvirt/driver.py", line 1365, in _create_image
    project_id=instance[\'project_id\'])
  File "/home/timjr/openstack/nova/app/nova/virt/libvirt/imagebackend.py", line 131, in cache
    *args, **kwargs)
  File "/home/timjr/openstack/nova/app/nova/virt/libvirt/imagebackend.py", line 181, in create_image
    if size and size < disk.get_disk_size(base):
  File "/home/timjr/openstack/nova/app/nova/virt/disk/api.py", line 115, in get_disk_size
    size = images.qemu_img_info(path)[\'virtual size\']
  File "/home/timjr/openstack/nova/app/nova/virt/images.py", line 50, in qemu_img_info
    \'qemu-img\', \'info\', path)
  File "/home/timjr/openstack/nova/app/nova/utils.py", line 210, in execute
    cmd=\' \'.join(cmd))

I have a fix I'll submit.