Fix polling timeout: use linked cancellation token in poll loop

The CancellationTokenSource with timeout was created but the loop and
Task.Delay used the original token instead, causing infinite polling
when ingestion status never reached a terminal state.

Author: monishkadas-ms

src/Services/IKustoIngestionService.cs

@@ -57,7 +57,7 @@ protected static async Task<IngestionStatus> PollIngestionStatus(IKustoIngestion
             var cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
             cts.CancelAfter(TimeSpan.FromMinutes(ingestionTimeoutMinutes));
             IngestionStatus ingestionStatus = null;
-            while (!cancellationToken.IsCancellationRequested)
+            while (!cts.Token.IsCancellationRequested)
             {
                 ingestionStatus = queuedIngestResult.GetIngestionStatusBySourceId(sourceId);
                 if (ingestionStatus.Status == Status.Succeeded
@@ -67,7 +67,7 @@ protected static async Task<IngestionStatus> PollIngestionStatus(IKustoIngestion
                 {
                     break;
                 }
-                await Task.Delay(TimeSpan.FromSeconds(pollIntervalSeconds), cancellationToken);
+                await Task.Delay(TimeSpan.FromSeconds(pollIntervalSeconds), cts.Token);
             }
             return ingestionStatus;
         }