image-guide: Update image link for openSUSE
image-guide: Update image link for openSUSE

There are multiple images for openSUSE available. Use the official
one.

Change-Id: Ib27d188351daa500aed37131aecb2071109f5b31

openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals