[autotest] Only stage test_suites in create_suite_job.

This reverts commit ecc0b7086ab66557b0009fc8d0765710fc593b41, with some
fixed unitttests.

TEST=unit
BUG=None

Change-Id: I250f3204fdd5fb0fef8a10fa6dcb27f9bd041994
Reviewed-on: https://chromium-review.googlesource.com/174246
Reviewed-by: Alex Miller <milleral@chromium.org>
Commit-Queue: Alex Miller <milleral@chromium.org>
Tested-by: Alex Miller <milleral@chromium.org>
diff --git a/frontend/afe/site_rpc_interface.py b/frontend/afe/site_rpc_interface.py
index f536c75..7d088de 100644
--- a/frontend/afe/site_rpc_interface.py
+++ b/frontend/afe/site_rpc_interface.py
@@ -129,7 +129,7 @@
     ds = dev_server.ImageServer.resolve(build)
     timings[constants.DOWNLOAD_STARTED_TIME] = formatted_now()
     try:
-        ds.trigger_download(build, synchronous=False)
+        ds.stage_artifacts(build, ['test_suites'])
     except dev_server.DevServerException as e:
         raise error.StageBuildFailure(
                 "Failed to stage %s for %s: %s" % (build, board, e))