atomic: only create new ref if needed
    
    If ostree_install_ref and ostree_update_ref are the same, as is the
    case for rawhide, then there is no reason to create a new ref. This
    is actually causing failures in rawhide right now.
    
    Having this setup will allow us to have the same configs in rawhide
    and branched where we do need separate install/update ref.
    
    Signed-off-by: Dusty Mabe <dusty@dustymabe.com>