[autotest] Create dynamic_suite child jobs with parent_job_id

Child jobs of a dynamic_suite call are now created with appropriate
parent_job_id pointing back at the suite job.

BUG=chromium-os:38253
TEST=Kick of a suite with run_suite.py. Child jobs have correct parent
job id, as seen in job detail view.

Change-Id: Ie45aac1b741b1282ddf792812480bc1f4d35278a
Reviewed-on: https://gerrit.chromium.org/gerrit/43583
Reviewed-by: Alex Miller <milleral@chromium.org>
Tested-by: Aviv Keshet <akeshet@chromium.org>
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
Commit-Queue: Aviv Keshet <akeshet@chromium.org>
diff --git a/frontend/afe/models.py b/frontend/afe/models.py
index 456b0bb..f4a9e31 100644
--- a/frontend/afe/models.py
+++ b/frontend/afe/models.py
@@ -1149,7 +1149,8 @@
             parse_failed_repair=options.get('parse_failed_repair'),
             created_on=datetime.now(),
             drone_set=drone_set,
-            parameterized_job=parameterized_job)
+            parameterized_job=parameterized_job,
+            parent_job=options.get('parent_job_id'))
 
         job.dependency_labels = options['dependencies']