tests: Add reproducer for #524

see this comment:
https://github.com/osbuild/osbuild-composer/issues/524#issuecomment-632017769

depending on the answer we should probably add more tests for
dnf-json too.

cmd/osbuild-tests/main_test.go

@@ -29,7 +29,8 @@ func TestComposeCommands(t *testing.T) {
 
 	bp := blueprint.Blueprint{
 		Name:        "empty",
-		Description: "Test empty blueprint in toml format",
+		Description: "Test blueprint in toml format",
+		Packages: []blueprint.Package{{Name: "bash", Version: "*"}},
 	}
 	pushBlueprint(t, &bp)
 	defer deleteBlueprint(t, &bp)