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
(cherry picked from commit 0adbbcf9f44367cb840c8786b05c35c63d7d2f41)
Merge "Fixes wrong values in get_glance_image_attrs" into stable/havana