Prevent kill_timeout greater than progress_deadline

.changelog/16761.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+core: Prevent `task.kill_timeout` being greater than `update.progress_deadline`
+```

nomad/structs/structs.go

@@ -5136,6 +5136,12 @@ func (u *UpdateStrategy) IsEmpty() bool {
 		return true
 	}
 
+	// When the Job is transformed from api to struct, the Update Strategy block is
+	// copied into the existing task groups, the only things that are passed along
+	// are MaxParallel and Stagger, because they are enforced at job level.
+	// That is why checking if MaxParallel is zero is enough to know if the
+	// update block is empty.
+
 	return u.MaxParallel == 0
 }
 
@@ -6708,6 +6714,8 @@ func (tg *TaskGroup) Validate(j *Job) error {
 		mErr.Errors = append(mErr.Errors, outer)
 	}
 
+	isTypeService := j.Type == JobTypeService
+
 	// Validate the tasks
 	for _, task := range tg.Tasks {
 		// Validate the task does not reference undefined volume mounts
@@ -6727,6 +6735,15 @@ func (tg *TaskGroup) Validate(j *Job) error {
 			outer := fmt.Errorf("Task %s validation failed: %v", task.Name, err)
 			mErr.Errors = append(mErr.Errors, outer)
 		}
+
+		// Validate the group's Update Strategy does not conflict with the Task's kill_timeout for service type jobs
+		if isTypeService && tg.Update != nil {
+			if task.KillTimeout > tg.Update.ProgressDeadline {
+				mErr.Errors = append(mErr.Errors, fmt.Errorf("Task %s has a kill timout (%s) longer than the group's progress deadline (%s)",
+					task.Name, task.KillTimeout.String(), tg.Update.ProgressDeadline.String()))
+			}
+		}
+
 	}
 
 	return mErr.ErrorOrNil()