Fix problem in order and adjustment model specs by fixing the order.adjustment association
Fix problem in order and adjustment model specs by fixing the order.adjustment association

This fix was taken from spree 2.1  here https://github.com/spree/spree/commit/3fa44165c7825f79a2fa4eb79b99dc29944c5d55

openfoodfoundation/openfoodnetwork,Matt-Yorkley/openfoodnetwork,openfoodfoundation/openfoodnetwork,mkllnk/openfoodnetwork,mkllnk/openfoodnetwork,lin-d-hop/openfoodnetwork,mkllnk/openfoodnetwork,openfoodfoundation/openfoodnetwork,mkllnk/openfoodnetwork,openfoodfoundation/openfoodnetwork,Matt-Yorkley/openfoodnetwork,Matt-Yorkley/openfoodnetwork,Matt-Yorkley/openfoodnetwork,lin-d-hop/openfoodnetwork,lin-d-hop/openfoodnetwork,lin-d-hop/openfoodnetwork