Attempt to fix unit test

Author: niemyjski

src/Exceptionless/Plugins/Default/1010_DuplicateCheckerPlugin.cs

@@ -50,7 +50,7 @@ public void Run(EventPluginContext context) {
                     return;
                 }
 
-                DateTimeOffset repeatWindow = DateTimeOffset.UtcNow.Subtract(_interval);
+                var repeatWindow = DateTimeOffset.UtcNow.Subtract(_interval);
                 if (_processed.Any(s => s.Item1 == hashCode && s.Item2 >= repeatWindow)) {
                     context.Log.FormattedTrace(_logSourceType, "Adding duplicate event: {0} with hash: {1} to cache for later submission.", context.Event.Message, hashCode);
                     // This event is a duplicate for the first time, lets save it so we can delay it while keeping count

test/Exceptionless.Tests/Plugins/PluginTests.cs

@@ -844,8 +844,9 @@ public void VerifyDeduplicationMultithreaded() {
                     duplicateCheckerPlugin.Run(context);
                 });
 
-                while (!result.IsCompleted)
-                    Thread.Sleep(1);
+                while (!result.IsCompleted) {
+                    Thread.Yield();
+                }
             }
 
             Thread.Sleep(150);