Fix hang-on-failure in sync_workspace (#880)

Summary:
Pull Request resolved: #880

Previously, when doing an rsync-based code sync, we'd hang waiting for
the rsync server proxy to finish after the rsync clients had already failed
and reported back errors via the reply port.

Fix to fail fast on any failure.

Reviewed By: highker

Differential Revision: D80267334

fbshipit-source-id: 5bcf02834799e80d0e2d6ae57046fdd1a7434af5

Author: andrewjcg

monarch_hyperactor/src/code_sync/manager.rs

@@ -416,7 +416,7 @@ pub async fn code_sync_mesh(
         }
     };
 
-    let (res1, res2) = futures::future::join(
+    let ((), ()) = try_join!(
         method_fut,
         // This async task will cast the code sync message to workspace owners, and process any errors.
         async move {
@@ -450,15 +450,9 @@ pub async fn code_sync_mesh(
                 .try_collect_or_stash::<()>(&mut errs);
             Ok(errs.into_result()?)
         },
-    )
-    .await;
-
-    // Combine code sync handler and cast errors into one.
-    let mut errs = ErrorStash::<_, _, anyhow::Error>::new(|| "code sync failed");
-    [res1, res2]
-        .into_iter()
-        .try_collect_or_stash::<()>(&mut errs);
-    Ok(errs.into_result()?)
+    )?;
+
+    Ok(())
 }
 
 #[cfg(test)]