Don't block task queue for queued update task when there are longer running tasks

Fixes #7538

Co-Authored-By: Mark McDowall <markus101@users.noreply.github.com>

src/NzbDrone.Core/Download/ProcessMonitoredDownloadsCommand.cs

@@ -5,5 +5,7 @@ namespace NzbDrone.Core.Download
     public class ProcessMonitoredDownloadsCommand : Command
     {
         public override bool RequiresDiskAccess => true;
+
+        public override bool IsLongRunning => true;
     }
 }

src/NzbDrone.Core/Indexers/RssSyncCommand.cs

@@ -1,9 +1,11 @@
-using NzbDrone.Core.Messaging.Commands;
+using NzbDrone.Core.Messaging.Commands;
 
 namespace NzbDrone.Core.Indexers
 {
     public class RssSyncCommand : Command
     {
         public override bool SendUpdatesToClient => true;
+
+        public override bool IsLongRunning => true;
     }
 }

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

@@ -27,6 +27,7 @@ public virtual bool SendUpdatesToClient
         public virtual bool RequiresDiskAccess => false;
         public virtual bool IsExclusive => false;
         public virtual bool IsTypeExclusive => false;
+        public virtual bool IsLongRunning => false;
 
         public string Name { get; private set; }
         public DateTime? LastExecutionTime { get; set; }

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

@@ -176,6 +176,11 @@ public bool TryGet(out CommandModel item)
                         queuedCommands = queuedCommands.Where(c => !exclusiveTypes.Any(x => x == c.Body.Name));
                     }
 
+                    if (startedCommands.Any(x => x.Body.IsLongRunning))
+                    {
+                        queuedCommands = queuedCommands.Where(c => !c.Body.IsExclusive);
+                    }
+
                     var localItem = queuedCommands.OrderByDescending(c => c.Priority)
                         .ThenBy(c => c.QueuedAt)
                         .FirstOrDefault();