Load balancing backoffice: Add missing id to distributed jobs when updating (#20642)

* Add ID when updating background job

* Reduce default period to 5 seconds

* Apply suggestions from code review

Co-authored-by: Andy Butland <abutland73@gmail.com>

---------

Co-authored-by: Andy Butland <abutland73@gmail.com>

src/Umbraco.Infrastructure/Models/DistributedBackgroundJobModel.cs

@@ -5,6 +5,11 @@
 /// </summary>
 public class DistributedBackgroundJobModel
 {
+    /// <summary>
+    /// The id of the job.
+    /// </summary>
+    public int Id { get; set; }
+
     /// <summary>
     /// Name of job.
     /// </summary>