Fix race condition in TaskThrottler (#159)

We waited for tasks to complete inside the loop, which meant that if cancelation of the loop was requested while it was in the part of the code after that (for example waiting on the mutex), they would never be awaited.

There is no real reason to wait inside the loop, we can just wait outside it, it is effectively the same.

Cognite.Common/TaskThrottler.cs

@@ -319,8 +319,6 @@ private async Task Run()
                         catch (TaskCanceledException)
                         {
                         }
-
-
                     }
                     else
                     {
@@ -338,17 +336,11 @@ await CommonUtils
                     _taskCompletionEvent.Reset();
                 }
 
-
                 lock (_lock)
                 {
                     if (_quitOnFailure && _runningTasks.Any(result => result.Task != null && result.Task.IsFaulted)) break;
                 }
 
-                if (_source.IsCancellationRequested || _generators.IsCompleted)
-                {
-                    await Task.WhenAll(_runningTasks.Select(result => result.Task)).ConfigureAwait(false);
-                }
-
                 lock (_lock)
                 {
                     var now = DateTime.UtcNow;
@@ -367,6 +359,10 @@ await CommonUtils
                         || result.Task.IsFaulted);
                 }
             }
+
+            await Task.WhenAll(
+                _runningTasks.Select(result => result.Task)
+                .Where(task => task != null && !task.IsCompleted)).ConfigureAwait(false);
         }
 
         /// <summary>