Fix race condition with database reset (#804)

* Wait for garbage collection to be finished before creating a new DB

* Prevent DB reset while inflight List requests

* Rename cacheFor to cacheForLocked

* Rename Reset to Stop

* Mention DoneWithCache in README

* Add RunGC to ByOptionsLister interface

pkg/sqlcache/informer/listoption_indexer_test.go

@@ -100,6 +100,8 @@ func makeListOptionIndexer(ctx context.Context, opts ListOptionIndexerOptions, s
 		return nil, "", err
 	}
 
+	go listOptionIndexer.RunGC(ctx)
+
 	return listOptionIndexer, dbPath, nil
 }