parallel-debian: Exclude plymouth
parallel-debian: Exclude plymouth

Otherwise the boot will stall if there's no plymouth in the
target image.

resin-io/ostree,GNOME/ostree,gatispaeglis/ostree,sujitfulse/ostree,leandrosansilva/ostree,resin-io/ostree,leandrosansilva/ostree,resin-io/ostree,resin-io/ostree,leandrosansilva/ostree,gatispaeglis/ostree,gatispaeglis/ostree,GNOME/ostree,GNOME/ostree,gatispaeglis/ostree,GNOME/ostree,leandrosansilva/ostree,sujitfulse/ostree,GNOME/ostree,sujitfulse/ostree,leandrosansilva/ostree,resin-io/ostree,sujitfulse/ostree,gatispaeglis/ostree,sujitfulse/ostree,gatispaeglis/ostree