tests/metalink: Add a case with nested unknown elements
tests/metalink: Add a case with nested unknown elements

leandrosansilva/ostree,GNOME/ostree,leandrosansilva/ostree,gatispaeglis/ostree,leandrosansilva/ostree,sujitfulse/ostree,sujitfulse/ostree,leandrosansilva/ostree,GNOME/ostree,gatispaeglis/ostree,sujitfulse/ostree,gatispaeglis/ostree,leandrosansilva/ostree,GNOME/ostree,gatispaeglis/ostree,gatispaeglis/ostree,GNOME/ostree,GNOME/ostree,sujitfulse/ostree,gatispaeglis/ostree,sujitfulse/ostree