Merge pull request #19214 from CyrusNajmabadi/flushAllTask

Actually keep track of the task we've kicked off to flush all writes to disk.

src/Workspaces/Core/Desktop/Workspace/SQLite/SQLitePersistentStorage_WriteBatching.cs

@@ -37,7 +37,7 @@ internal partial class SQLitePersistentStorage
                 if (_flushAllTask == null)
                 {
                     var token = _shutdownTokenSource.Token;
-                    var delay =
+                    _flushAllTask =
                         Task.Delay(FlushAllDelayMS, token)
                             .ContinueWith(
                                 async _ => await FlushAllPendingWritesAsync(token).ConfigureAwait(false),