Update templates for Atomic (sub)variant renames
    
    Atomic was renamed AtomicHost, and Workstation Ostree was renamed
    AtomicWorkstation, for F28+. As we still have F26 and F27 images
    which will have the Atomic name, we duplicate those templates,
    but there should be no more 'Workstation Ostree' images, so we
    just rename those templates to the new name.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>