local backend: fix log been eaten when failed on execute region job (#47782)

close #47781

Author: D3Hunter

br/pkg/lightning/backend/local/local.go

@@ -1692,7 +1692,10 @@ func (local *Backend) doImport(ctx context.Context, engine common.Engine, region
 	if err != nil {
 		firstErr.Set(err)
 		workerCancel()
-		_ = workGroup.Wait()
+		err2 := workGroup.Wait()
+		if !common.IsContextCanceledError(err2) {
+			log.FromContext(ctx).Error("worker meets error", zap.Error(err2))
+		}
 		return firstErr.Get()
 	}