Use persisted duration for running jobs

Fixes #318

internal/graph/schema.resolvers.go

@@ -36,10 +36,7 @@ func (r *jobResolver) Tags(ctx context.Context, obj *schema.Job) ([]*schema.Tag,
 
 // ConcurrentJobs is the resolver for the concurrentJobs field.
 func (r *jobResolver) ConcurrentJobs(ctx context.Context, obj *schema.Job) (*model.JobLinkResultList, error) {
-	if obj.State == schema.JobStateRunning {
-		obj.Duration = int32(time.Now().Unix() - obj.StartTimeUnix)
-	}
-
+	// FIXME: Make the hardcoded duration configurable
 	if obj.Exclusive != 1 && obj.Duration > 600 {
 		return r.Repo.FindConcurrentJobs(ctx, obj)
 	}