[autotest] Reroute some RPCs called to a shard to master

create_job and create_suite_job RPCs should not be handled by a shard.
They should be redirected to the master.

BUG=chromium:503188
TEST=puppylab. Submit a dummy suite in a stumpy shard.

Change-Id: Ibe432655c677024e9eee1f4aca118ef6db7951f7
Reviewed-on: https://chromium-review.googlesource.com/281818
Reviewed-by: Mungyung Ryu <mkryu@google.com>
Commit-Queue: Mungyung Ryu <mkryu@google.com>
Tested-by: Mungyung Ryu <mkryu@google.com>
diff --git a/frontend/afe/site_rpc_interface.py b/frontend/afe/site_rpc_interface.py
index 7127265..3163b8a 100644
--- a/frontend/afe/site_rpc_interface.py
+++ b/frontend/afe/site_rpc_interface.py
@@ -119,6 +119,7 @@
     return (ds, timings)
 
 
+@rpc_utils.route_rpc_to_master
 def create_suite_job(name='', board='', build='', pool='', control_file='',
                      check_hosts=True, num=None, file_bugs=False, timeout=24,
                      timeout_mins=None, priority=priorities.Priority.DEFAULT,