[autotest] Make sync_send_file_to private

BUG=None
TEST=None

Change-Id: I3652d50fc94352a8ab4a3a2f509346a541ceaef0
Reviewed-on: https://chromium-review.googlesource.com/511764
Commit-Ready: Allen Li <ayatane@chromium.org>
Tested-by: Allen Li <ayatane@chromium.org>
Reviewed-by: Prathmesh Prabhu <pprabhu@chromium.org>
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
diff --git a/scheduler/drone_utility.py b/scheduler/drone_utility.py
index 5ba45e0..1abf220 100755
--- a/scheduler/drone_utility.py
+++ b/scheduler/drone_utility.py
@@ -368,9 +368,9 @@
                                (hostname, source_path, destination_path))
 
 
-    def sync_send_file_to(self, hostname, source_path, destination_path,
+    def _sync_send_file_to(self, hostname, source_path, destination_path,
                            can_fail):
-        logging.debug('sync_send_file_to. hostname: %s, source_path: %s, '
+        logging.debug('_sync_send_file_to. hostname: %s, source_path: %s, '
                       'destination_path: %s, can_fail:%s', hostname,
                       source_path, destination_path, can_fail)
         host = create_host(hostname)
@@ -399,7 +399,7 @@
 
     def send_file_to(self, hostname, source_path, destination_path,
                      can_fail=False):
-        self.run_async_command(self.sync_send_file_to,
+        self.run_async_command(self._sync_send_file_to,
                                (hostname, source_path, destination_path,
                                 can_fail))