test: add retry attribute to CancelLongTaskShouldSucceed test (#863)

# Motivation

Avoid potential crash during the **Common Tests**.

# Description

Implement a retry attribute so that it can retry 3 times in case of a
crash.

# Testing

None

# Impact

Avoid unexpected crash when pushing a commit on Core.

# Additional Information

None

# Checklist

- [X] My code adheres to the coding and style guidelines of the project.
- [ ] I have performed a self-review of my code.
- [ ] I have commented my code, particularly in hard-to-understand
areas.
- [ ] I have made corresponding changes to the documentation.
- [ ] I have thoroughly tested my modifications and added tests when
necessary.
- [ ] Tests pass locally and in the CI.
- [ ] I have assessed the performance impact of my modifications.

Common/tests/Pollster/PollsterTest.cs

@@ -654,6 +654,7 @@ await testServiceProvider.TaskTable.GetTaskStatus(taskSubmitted,
 
   [Test]
   [Timeout(30000)]
+  [Retry(3)]
   public async Task CancelLongTaskShouldSucceed()
   {
     var mockPullQueueStorage    = new SimplePullQueueStorageChannel();