shill: Sort headers alphabetically (build/include_alpha)

We are going to enable build/include_alpha linter warning soon,
so in preparation for this, fixed the warnings in shill.

BUG=None
TEST=cpplint.py --filter=-build/include_order,+build/include_alpha shill/*

Change-Id: I113ed7f9dd3f465a3f660599320cdb434e7cc214
Reviewed-on: https://chromium-review.googlesource.com/209636
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/glib_io_ready_handler.h b/glib_io_ready_handler.h
index 9836085..d18e73b 100644
--- a/glib_io_ready_handler.h
+++ b/glib_io_ready_handler.h
@@ -5,8 +5,8 @@
 #ifndef SHILL_GLIB_IO_READY_HANDLER_H_
 #define SHILL_GLIB_IO_READY_HANDLER_H_
 
-#include <stdio.h>
 #include <glib.h>
+#include <stdio.h>
 
 #include <base/callback.h>