Fixes wrong values in get_glance_image_attrs

The output of the glance show command in get_glance_image_attrs
does not get properly converted while being added to the
attrs array.

Change-Id: Ibe503b24ae3bfa10944537d5deaa068a01eaa5f3
Closes-Bug: #1199513
Merge "Fixes wrong values in get_glance_image_attrs"