update_engine: fixed warnings from cpplint

Fixed all the cpplint warnings in update engine.

BUG=None
TEST=Unit tests still pass.

Change-Id: I285ae858eec8abe0b26ff203b99a42a200ceb71c
Reviewed-on: https://chromium-review.googlesource.com/204027
Reviewed-by: Alex Vakulenko <[email protected]>
Tested-by: Alex Vakulenko <[email protected]>
Commit-Queue: Alex Vakulenko <[email protected]>
diff --git a/connection_manager_unittest.cc b/connection_manager_unittest.cc
index c495fbf..ca6e256 100644
--- a/connection_manager_unittest.cc
+++ b/connection_manager_unittest.cc
@@ -2,11 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <set>
+#include <string>
+
 #include <base/logging.h>
 #include <chromeos/dbus/service_constants.h>
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
-#include <string>
 
 #include "update_engine/connection_manager.h"
 #include "update_engine/fake_system_state.h"