[autotest] tko/parse: Do not cast afe_parent_job_id to str

The job_keyval is already str. The only case the cast was not a no-op
was when afe_parent_job_id was None. We want the value to be reported as
None in that case.

BUG=chromium:838708
TEST=None

Change-Id: Ic3be24fdbcaa6d87d41269da78f95ee986c43352
Reviewed-on: https://chromium-review.googlesource.com/1043089
Commit-Ready: Prathmesh Prabhu <pprabhu@chromium.org>
Tested-by: Prathmesh Prabhu <pprabhu@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Reviewed-by: Shuhei Takahashi <nya@chromium.org>
diff --git a/tko/parse.py b/tko/parse.py
index b734367..ac2221e 100755
--- a/tko/parse.py
+++ b/tko/parse.py
@@ -348,8 +348,8 @@
 
     job.afe_job_id = tko_utils.get_afe_job_id(jobname)
     job.skylab_task_id = tko_utils.get_skylab_task_id(jobname)
-    job.afe_parent_job_id = str(job_keyval.get(constants.PARENT_JOB_ID))
-    job.skylab_parent_task_id = str(job_keyval.get(constants.PARENT_JOB_ID))
+    job.afe_parent_job_id = job_keyval.get(constants.PARENT_JOB_ID)
+    job.skylab_parent_task_id = job_keyval.get(constants.PARENT_JOB_ID)
     job.build = None
     job.board = None
     job.build_version = None