fix: Fix flaky scaled scan fuzzer test (#11989)

Summary:
Pull Request resolved: #11989

The fuzzer test flakiness is due to the race between test thread and scaled controller close. This PR fixes the issue
by moving the driver index check after the controller close check

Reviewed By: tanjialiang

Differential Revision: D67727455

fbshipit-source-id: ba136ba86654104a7502bb3b0169cfd1a015ff8a

velox/exec/ScaledScanController.cpp

@@ -76,12 +76,12 @@ void ScaledScanController::updateAndTryScale(
   };
   {
     std::lock_guard<std::mutex> l(lock_);
-    VELOX_CHECK_LT(driverIdx, numRunningDrivers_);
-
     if (closed_) {
       return;
     }
 
+    VELOX_CHECK_LT(driverIdx, numRunningDrivers_);
+
     updateDriverScanUsageLocked(driverIdx, memoryUsage);
 
     tryScaleLocked(driverPromise);