omdb test is flaky because of the order of background tasks printed out

dev-tools/omdb/src/bin/omdb/nexus.rs

@@ -145,7 +145,9 @@ async fn cmd_nexus_background_tasks_show(
 ) -> Result<(), anyhow::Error> {
     let response =
         client.bgtask_list().await.context("listing background tasks")?;
-    let mut tasks = response.into_inner();
+    // Convert the HashMap to a BTreeMap because we want the keys in sorted
+    // order.
+    let mut tasks = response.into_inner().into_iter().collect::<BTreeMap<_, _>>();
 
     // We want to pick the order that we print some tasks intentionally.  Then
     // we want to print anything else that we find.