PR FIXUP - Move close of closing chan to within lock

Also removed the Do as it becomes pointless on this side of the lock.

datastore/memory/memory.go

@@ -117,15 +117,14 @@ func (d *Datastore) newBasicBatch() ds.Batch {
 }
 
 func (d *Datastore) Close() error {
-	d.closeOnce.Do(func() {
-		close(d.closing)
-	})
 	d.closeLk.Lock()
 	defer d.closeLk.Unlock()
 	if d.closed {
 		return ErrClosed
 	}
+
 	d.closed = true
+	close(d.closing)
 	close(d.commit)
 	return nil
 }