Include the implemented header first in all projects.

The Google C++ style guide dictates that foo.cc and foo_unittest.cc
should include foo.h in the first place, so missing headers in foo.h
are detected with a compile error of the module implementing them and
not when another module uses them.

This CL sweeps across all the .cc file in platform2 enforcing this.

BUG=None
TEST=cbuildbot amd64-generic

Change-Id: I41835835caba13f54c3c844ecf552eb0e47efa9d
Reviewed-on: https://chromium-review.googlesource.com/228894
Tested-by: Alex Deymo <deymo@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/mock_dns_server_tester.cc b/mock_dns_server_tester.cc
index 9f5232b..54955e8 100644
--- a/mock_dns_server_tester.cc
+++ b/mock_dns_server_tester.cc
@@ -2,11 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "shill/mock_dns_server_tester.h"
+
 #include <string>
 #include <vector>
 
 #include "shill/connection.h"
-#include "shill/mock_dns_server_tester.h"
 
 namespace shill {