[autotest] Endpoints for syncing jobs and hqes back to master

The status of jobs that were completed on a shard should be visible
in the master AFE, so a human can easily see which jobs have been run in one
central place.

This adds the functionality to the AFE to retrieve newer versions of
jobs and hqes from shards.

This is a newer version of CL:213901 which was reverted because of
http://crbug.com/418022.

BUG=418022
DEPLOY=apache, afe
TEST=Ran Suites

Change-Id: I3c9a35c78585a43d193874decbb7b16216b2c69a
Reviewed-on: https://chromium-review.googlesource.com/220141
Reviewed-by: Fang Deng <fdeng@chromium.org>
Tested-by: Jakob Jülich <jakobjuelich@chromium.org>
Commit-Queue: Jakob Jülich <jakobjuelich@chromium.org>

client/common_lib/error.py

diff --git a/client/common_lib/error.py b/client/common_lib/error.py
index 56c9421..1f664d9 100644
--- a/client/common_lib/error.py
+++ b/client/common_lib/error.py
@@ -635,6 +635,10 @@
     pass
 
 
+class UnallowedRecordsSentToMaster(Exception):
+    pass
+
+
 # This MUST remain at the end of the file.
 # Limit 'from error import *' to only import the exception instances.
 for _name, _thing in locals().items():