Feature: Thread-blocking task status completion

Thread can be blocked until a task completes (or a timeout period
elapses). Used to wait up to 3 seconds before redirecting to the
TaskStatus when downloading the Plugin Catalogue.

Disco.Services/Tasks/ScheduledTask.cs

@@ -90,6 +90,8 @@ namespace Disco.Services.Tasks
                 if (!this.Status.FinishedTimestamp.HasValue) // Scheduled Task Didn't Trigger 'Finished'
                     this.Status.Finished();
 
+                this.Status.Finally();
+
                 var nextTriggerTime = context.NextFireTimeUtc;
                 if (nextTriggerTime.HasValue)
                 { // Continuous Task