test: use system-first search for dbus interfaces

Use system-first search for inclusion of dbus interface headers.

Change-Id: I9953ca047c09c1003c86b1ffaf929698c157139c
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/test/test_config_parser.cpp b/test/test_config_parser.cpp
index 99effad..61432c2 100644
--- a/test/test_config_parser.cpp
+++ b/test/test_config_parser.cpp
@@ -1,12 +1,12 @@
 #include "config.h"
 
 #include "config_parser.hpp"
-#include "xyz/openbmc_project/Common/error.hpp"
 
 #include <exception>
 #include <fstream>
 #include <phosphor-logging/elog-errors.hpp>
 #include <stdexcept>
+#include <xyz/openbmc_project/Common/error.hpp>
 
 #include <gtest/gtest.h>