In disk_channel queues synchronously push to disk on shutdown (#18415) (#18788)

Partial Backport of #18415

Instead of using an asynchronous goroutine to push to disk on shutdown
just close the datachan and immediately push to the disk.

Prevents messages of incompletely flushed queues.

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

modules/queue/queue_bytefifo.go

@@ -195,9 +195,11 @@ loop:
 	}
 }
 
-var errQueueEmpty = fmt.Errorf("empty queue")
-var errEmptyBytes = fmt.Errorf("empty bytes")
-var errUnmarshal = fmt.Errorf("failed to unmarshal")
+var (
+	errQueueEmpty = fmt.Errorf("empty queue")
+	errEmptyBytes = fmt.Errorf("empty bytes")
+	errUnmarshal  = fmt.Errorf("failed to unmarshal")
+)
 
 func (q *ByteFIFOQueue) doPop() error {
 	q.lock.Lock()