garbage_collect: call fail_on_abort to abort GV when requested.

src/api2/admin/datastore.rs

@@ -630,7 +630,7 @@ fn start_garbage_collection(
         "garbage_collection", Some(store.clone()), "root@pam", to_stdout, move |worker|
         {
             worker.log(format!("starting garbage collection on store {}", store));
-            datastore.garbage_collection(worker)
+            datastore.garbage_collection(&worker)
         })?;
 
     Ok(json!(upid_str))