Default to 3 task threads like Sonarr/Lidarr

src/NzbDrone.Core/Messaging/Commands/CommandExecutor.cs

@@ -13,7 +13,7 @@ namespace NzbDrone.Core.Messaging.Commands
     {
         private const int THREAD_UPPER_BOUND = 10;
         private const int THREAD_LOWER_BOUND = 2;
-        private const int THREAD_LIMIT = 2;
+        private const int THREAD_LIMIT = 3;
 
         private readonly Logger _logger;
         private readonly IServiceFactory _serviceFactory;