Add a new test_list option sync_event_log

With this option disable, events will not get synced to server.

BUG=chrome-os-partner:20854
TEST=run syncshopfloor test, check factory.log has messages like
"Skipped syncing event logs Chunk(log_name='events', len=520, pos=12460)"

Change-Id: If64b03bd5ac091c7fd65fde4b8d5921609c08392
Reviewed-on: https://gerrit.chromium.org/gerrit/62323
Reviewed-by: Vic Yang <victoryang@chromium.org>
Commit-Queue: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
diff --git a/py/goofy/goofy.py b/py/goofy/goofy.py
index 17fab6f..995af52 100755
--- a/py/goofy/goofy.py
+++ b/py/goofy/goofy.py
@@ -1773,6 +1773,11 @@
     Args:
       chunks: A list of Chunk objects.
     '''
+    if not self.test_list.options.sync_event_log:
+      logging.info('Skipped syncing event logs %s',
+          ', '.join([str(chunk) for chunk in chunks]))
+      return
+
     first_exception = None
     exception_count = 0