Add a small buffer to DoMaintenanceAsync to account for system clock …

…drift, see if this fixes flakey ci test.

src/Foundatio/Queues/InMemoryQueue.cs

@@ -392,7 +392,9 @@ public override Task DeleteQueueAsync()
                 _logger.LogError(ex, "DoMaintenance Error: {Message}", ex.Message);
         }
 
-        return minAbandonAt;
+        // Add a tiny buffer just in case the schedule next timer fires early.
+        // The system clock typically has a resolution of 10-15 milliseconds, so timers cannot be more accurate than this resolution.
+        return minAbandonAt.SafeAdd(TimeSpan.FromMilliseconds(10));
     }
 
     public override void Dispose()