lib/repo: Properly list remotes of parent repos

This commit fixes an infinite loop that happens if you try to list the
remotes of a repo that has a parent repo set. It also adds a unit test
to ensure the right behavior, which is that both the child remotes and
parent remotes are listed.

Closes: #1366
Approved by: cgwalters

src/libostree/ostree-repo.c

@@ -1791,7 +1791,7 @@ _ostree_repo_remote_list (OstreeRepo *self,
   g_mutex_unlock (&self->remotes_lock);
 
   if (self->parent_repo)
-    _ostree_repo_remote_list (self, out);
+    _ostree_repo_remote_list (self->parent_repo, out);
 }
 
 /**